stuffing box for yachts

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Shaft Seals, Couplings, & Parts

Stuffing / packing boxes.

• Dripless Shaft Seals
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• Buck Algonquin / Hydrasearch
• C.S. Osborne & Co.

What You Should Know About Your Stuffing Box

The  stuffing box,  sometimes referred to as a  packing box  or a packing gland, has been around for many years; so many in fact, that some insist it was in use almost as far back as ancient mariners. We're not so sure about that, but regardless of the when, it is a well proven, reliable, and functional design. Most new boats since the year 2000 have shaft seals that require no packing, but sterndrive boats built before then have traditional stuffing boxes with packing.

The stuffing box is still an inexpensive method of sealing a rotating shaft when compared to the newer alternative system, especially in the larger sizes. A stuffing box does have some limitations, but so do many of the alternative shaft seals out there. One such limitation of the stuffing box is that it is not suitable for high-speed shafts.

This is not due to the stuffing box itself but rather the packing.  Stuffing box packing  has also seen its fair share of evolution and there are a few different choices out there, but they all have similar characteristics in common. The  stuffing box packing  is compressed to achieve the seal around the rotating shaft and the stationary housing. The sealing surface around the shaft is large and when the shaft turns, the surface friction creates undesirable heat.

This heat eventually deteriorates the surface of the shaft and reduces the effectiveness of the bearing packing. To mitigate the heat buildup, it is important to adjust the stuffing box correctly so that during operation some liquid passes by the seal to aid in lubricating the seal and reduce the heat buildup; and that when idle, no liquid passes by the seal. This can be done with constant attention, which is not always possible, and that leads to an annoying, constantly dripping shaft seal.

Aside from a lack of constant attention being a cause for stuffing box ineffective performance, other contributing factors are the condition of the shaft surface, the shaft alignment, and the condition of the bearings.  Interior shafting components such as the shaft coupling is also critical in ensuring that a shaft runs true. Shaft vibration, among other detriments, contributes to shaft sealing failure. Installing a flexible coupling reduces vibrations and can compensate for slight misalignment issues.

A stuffing box and the stuffing box packing will require maintenance, as the rubber hose will deteriorate over time and the propeller shaft seal will diminish as the packing wears out. Other hardware might need replacing as well, and thankfully there is still manufacturer support for even some of the oldest propeller shaft seals out there.

Alternatives to a shaft sealing with stuffing is a  dripless shaft seal.  There are a few types on the market with all achieving the same result--that being a dripless shaft seal. So, if a new stuffing box, shaft sealing, propeller shaft seal or other parts is on the maintenance list, take a look at what we have here for you at Go2marine.

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Servicing Your Stuffing Box

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Stuffing Box

If your boat has inboard power, odds are it is fitted with a stuffing box to provide a watertight seal for the propeller shaft. Stuffing boxes are also used to seal rudder stocks that penetrate the hull below the waterline.

In principle a stuffing box is identical to the packing nut on a common faucet. Its primary components are a threaded sleeve and a hollow nut through which the shaft passes. The sleeve — or sometimes the nut — is filled with rings of braided square flax rope that has been heavily impregnated with wax and lubricants. Tightening the nut compresses this packing against the shaft, forming a watertight seal while still allowing the shaft to turn.

Water is required to lubricate conventional packing, so a properly adjusted stuffing box can be watertight when the shaft is stopped, but it must drip when the shaft is turning. Two or three drops per minute are adequate. It is not uncommon to see stuffing boxes leak at a much higher rate. This doesn't harm the shaft or the stuffing box, but the spinning shaft will sling this excess flow all over the engine compartment, leading to rampant corrosion of the shaft coupling, the transmission housing, and everything else getting sprayed. Even more disastrous, it puts an unattended boat at risk of sinking. If your stuffing box leaks more than 8 or 10 drops a minute, it needs servicing. Tightening the stuffing box nut a half turn is all that is required to reduce the leak, but the location of the stuffing box can render this job far more difficult than it should be. Access can be especially challenging in boats with V-drives and in sailboats.

The first step in stuffing box adjustment, then, is to figure out how to get two wrenches on the box--one for the lock nut and one for the adjusting nut — and how to position yourself so that you can pull on one while pushing on the other, and vice versa. You can use pipe wrenches to turn the nuts, but adjustable packing nut wrenches tend to be easier to handle in confined spaces. If the stuffing box is above a deep bilge, tie a retaining line to the wrenches before you start. With your wrenches on both nuts, hold the adjusting nut and turn the locknut clockwise to release it. Back this nut off a couple of turns. Now turn the adjusting nut clockwise until the dripping just stops.

CAUTION: Some stuffing boxes are rigidly attached to the hull, but most are connected to the shaft tube with a length of flexible hose. You do not want to twist this hose or twist the stuffing box inside the hose. If the adjusting nut does not turn easily, use a pipe wrench on the stuffing box flange — located just forward of the hose — to keep the box from turning with the nut. If the box is corroded, back off the adjusting nut several turns and wire brush the box threads bright before making the adjustment. Give threads and nuts a heavy coat of Boeshield T-9 (or some other corrosion blocker) to avoid this problem in the future.

After you make this initial adjustment, you are going to need to check the drip rate with the shaft turning. You can do this either with the boat underway or with the transmission engaged in forward and the boat securely tied in the slip. With the help of a flashlight — and a mirror if you need one — count the drops per minute. If it is more than two, tighten the adjusting nut slightly. If you cannot make this adjustment without putting body parts or clothing in dangerous proximity to the spinning shaft, stop the engine, make the adjustment, then restart it to check the drips. When the drip rate is one or two drops per minute, stop the engine. Hold the adjusting nut securely so that you do not alter the setting, then tighten the locknut against it. Before you extract yourself from your access position, carefully check the strap clamps that attach the hose to the stuffing box and to the stern tube. These inevitably corrode at the bottom, so you may need a mirror to check them. Better yet, release each one and rotate it to view all sides before retightening. Do this one clamp at a time.

After the packing nut has been tightened a few times, the packing gets so compressed that it becomes hard enough to actually wear a groove in the shaft — a condition you want to avoid. In a powerboat used regularly, the shaft packing should be replaced at least every other year. Sailboats may not need to have the packing replaced for five years or more, but when the stuffing box starts requiring frequent adjustment or if it begins to feel warm, it's time.

Repacking is straightforward. Hold the packing nut while you release the lock nut, then unscrew the adjusting nut completely to open the box. You must dig out ALL of the old packing. The easiest way to do this is with a corkscrew-like pick designed specifically for this task, but a sharpened piece of stiff wire bent 90 degrees at the end will also do the job. Take care not to scratch the shaft with either tool.

If the old packing comes out relatively intact, use it to determine what size packing you need. If it comes out as shapeless wads of fluff, then measure the space between the shaft and the inside of the packing nut to determine the correct flax size. Multiply the diameter of your shaft by 14 to get the approximate number of inches you need for 4 layers of new packing — usually sufficient.

A common mistake is winding the new packing around the shaft as a continuous piece. Packing installed this way will not seal properly. It must instead be installed as a series of stacked rings. This requires cutting the packing into lengths that just encircle the shaft with ends touching. The easy way to do this is to wrap the packing around the shaft in some accessible location and cut across the overlap with a razor knife. Curl one of your cut lengths into a ring around the shaft and push it into the stuffing box. Tamp it evenly with a small dowel or a blunt screwdriver to push it all the way to the bottom of the box. Push a second ring into the stuffing box on top of the first one, staggering the joint about 120 degrees. Add a third layer, then a fourth, each time staggering the joint. If you don't seem to have room for the fourth layer, hand tighten the adjusting nut to force the other rings deeper, then remove it again to see if this made room for an additional ring of flax. When the box is full — but not so full that the adjusting nut doesn't thread on easily — adjust it to drip two or three times per minute, as previously outlined. You will need to check this setting after the first couple of hours of use; some tightening is usually required.

Because you remove the old packing before installing new, and it is the packing that is keeping the ocean out of your boat, it should be out of the water when you do this job. If you must do it with the boat afloat, have the new packing ready to install as soon as the old is out, and drape a towel over the stuffing box to deflect the incoming flood into the bilge, where your bilge pump should handle it without difficulty. You can make the task less frantic by sealing the shaft from the outside with plumbers putty, but you will have to go into the water twice to do this, once to put the putty around the shaft, and a second time to remove it. Do not turn the shaft while the putty is in place or you will break its seal, and make sure you clean out ALL the putty when you are finished since both the stern bearing and the shaft seal depend on water flow for lubrication.

Drip-Less Packing

An alternative to conventional braided packing is Drip-Less moldable packing. The advantage of this type of packing is that it is self lubricating, which eliminates the necessity of letting the stuffing box drip. Drip-Less packing requires two retainer rings of conventional packing. You install a ring of conventional packing, then push Dripless Packing into the box until it is about three-quarters full. A second ring of conventional packing completes the job. Tighten the nut just enough to stop the box from dripping. This type of packing runs hotter than water-lubricated flax, and over tightening will generate excessive heat. The stuffing box should not be too hot to touch. Low-friction packing is six to ten times more expensive than flax, but because it rarely needs adjustment, it can be a good choice for a stuffing box that is particularly difficult to service.

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Contributor, BoatUS Magazine

Don Casey has been one of the most consulted experts on boat care and upgrades for 30 years, and is one of the BoatUS Magazine's panel of experts. He and his wife cruise aboard their 30-footer part of the year in the eastern Caribbean. His books include Don Casey's Complete Illustrated Sailboat Maintenance Manual, and the recently updated This Old Boat, the bible for do-it-yourself boaters.

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Re-Packing A Traditional Stuffing Box

The Stuffing Box (click any image to see a larger version)

While digging around in some old boat parts boxes I found a stuffing box from an older sailboat. I though it would be a good time to rig it up in my shop and illustrate how to replace the packing material inside one of these tried & true work horse style stuffing boxes. Stuffing boxes are also called stuffing glands, packing glands or packing boxes but they are really all the same thing.

For illustrative purposes I cleaned the stuffing box of it’s oxidation and grime with my a stainless wire brush. I used a piece of 1″ diameter stainless steel as my makeshift prop shaft to complete the picture and present this as it would look inside a boat.

In this photo what you are actually seeing are two nuts not just one. The larger of the two is where the flax resides. The thin nut, on the left, is the locking-nut . Once re-packed, & properly adjusted, you lock these nuts together with two large wrenches.

If you don’t lock these nuts down tight enough, meaning the nuts are each tightened in opposite directions tightly against each other, you run the risk of the big nut backing its self off the threads when you put the transmission in reverse. Over the decades there have been more than a few boats sunk by improper adjustments of the stuffing box nuts.

IMPORTANT: I am not advocating the use of perforated hose clamps on a stuffing box. I would strongly urge you to use non-perforated AWAB 316 SS hose clamps instead. This article was done in my shop and I used what was easily on hand to make the article work. On the day I shot this I did not have any  non-perforated AWAB hose clamps to fit this hose. The article is about re-packing the stuffing box not about the hose clamps.

Stuffing Box Wrenches

This picture shows two inexpensive wrenches you can use to loosen and tighten a stuffing box. One wrench is a traditional pipe wrench and the other is a spanner wrench designed for a sink drain. Both of these wrenches are available at Home Depot or any hardware store.

I find it easier to use the pipe wrench on the small & thin locking nut and the spanner wrench on the big nut. It’s very important to use wrenches that fit the nuts well. Water pump pliers will, in many cases, not work very well or will not get the nuts tight enough after adjustment. Use good wrenches and not pliers for safety’s sake.

TIP: While I show these wrenches as wrenches you can use I would urge you to purchase as set of proper stuffing box wrenches for your particular box. Buck Algonquin and others sell packing box wrenches and they can be purchased from vendors such as Hamilton Marine.

If you’ve tried the above method and the nuts don’t break apart use a little bit of PB Blaster or Kroil. Products such as WD40  DO NOT WORK WELL AS A PENETRATING OIL . I can’t stress enough how much of a difference there is between a product like PB Blaster or Kroil and lousy penetrating products such as WD40.

Here’s a direct quote from a reader who used this article for directions. Unfortunately after three hours, Liquid Wrench, and a broken tool he gave up and emailed me for advice:

Begin Quote:

“I knew where the cap and the locking nut were, I just couldn’t budge them. I went out and bought some of the PB Blaster you advised me about and sprayed it on. Ten minutes after spraying it broke loose. PBB rules. Thanks”

Tightening & Loosening

Here’s another view of the wrenches and the process.

* When loosening the nuts the two wrenches are moved towards each other

* When tightening the nuts the wrenches (as shown here) are moved away from each other.

Broken Free

In this photo it’s much easier to see the two distinct nuts. The thin one on the left is the locking nut and the big thick nut on the right is the packing nut.

This photo shows the threaded male end of bronze stuffing box and the packing-nut or the female end of the stuffing box separated from the male end. The white PVC pipe on the left is my dummy-mock-up of a vessels fiberglass shaft log.

The rubber hose connects the bronze stuffing box to the boats shaft log and needs to be replaced periodically .

If this rubber hose cracks, deteriorates or starts leaking, it can sink your boat. Most references suggest replacing the rubber stuffing box hose every seven to ten years.

Correct Hose vs. Incorrect Hose

If you happen have your shaft out, this makes for an opportune time to replace your stuffing box hose as well.

The thicker hose on top is specifically made for stuffing boxes. It’s a robust 6 ply hose , and meant to take the abuses of a drive train installation. The stuffing box hose on top is made by Buck Algonquin. Buck Algonquin a US manufacturer of quality bronze packing boxes and other drive-line components.

This Buck Algonquin hose, sized for a 1 3/4″ shaft log, can be purchased from Hamilton Marine for about $9.00 or less.

IMPORTANT: Please do not use wet exhaust hose, as  shown below the Buck Algonquin hose. There is a big difference between actual stuffing box hose and a wet exhaust or plumbing hose. Seek out hose specifically made for stuffing boxes.

If you can’t find Buck Algonquin hose in the size you need you could use a minimum of 4 ply non-wire reinforced hose. Please do not use 2 ply or 2 ply wire reinforced hose. A stuffing box is no place for wire reinforced hose.

WRONG HOSE… D’oh……

There are vast difference in hoses and most are not at all suitable for a stuffing box application. I take many pictures of bad installations but a reader sent me this one. This one takes the cake.

• Use the right hose
• Replace on a 7-10 year +/- cycle

Please do not use the wrong hose. This boat came darn close to sinking. Use 4 ply minimum, non-wire reinforced hose. The Buck Algonquin product is six-ply .

Incorrectly Clamped

Double hose clamps won’t do any good, and can actually be detrimental, if they are not clamping anything but air. Look at the inner clap on the shaft log. It is not clamping anything but rubber. Oops……

Please be sure your hose clamps are clamping what they are intended to clamp .

Stuffing Nut Shown WIth Old Flax Still In It

When you are replacing your packing you will most likely never see this view unless you remove the transmission coupling and take the nut off. When removing the flax, with a pick, this is what you are trying to dig out! I took this photo to show the female nut with the old flax still in it. You can see the shiny surface where it meets the shaft and the thickness (3/16) of the flax its self.

Today we are lucky to have more availability than the old stand-by antique plant based packing materials such as flax packing . Flax packing is prone to rot, expansion & contraction, which messe with adjustment, and has a higher propensity to score shafting.

Packing Material Types:

Flax Packing – This packing material is derived from flax plants and they require a higher drip rate for lubrication. Most flax packing materials are impregnated with paraffin/wax and animal lard. Some flax packing materials are impregnated with Teflon. Kind of like putting lip-stick on a pig. This type of packing absorbs water, swells/shrinks and is not well suited for vessels that get hauled for winter storage. It is an inexpensive packing but low in performance.

Synthetic Packing – While often called “ synthetic packing ” the individual yarns the braid is made from are most often made of acrylic. These packing materials absorb less water, are less prone to rot and are quite often impregnated with Teflon, paraffin or lard as a lube. The have a lower temperature performance rating than Teflon yarns and sit in-between flax and Teflon for performance. They require a medium drip-rate for optimal lubrication.

Teflon Packing- This packing material does not swell, does not rot and will stay adjusted longer. This type of packing is optimal for boats that are dry stored yearly and haul / launch usually requires no additional adjustments due to dry-out and re-absorb.. They also are available with added lubrication . These packing products are galvanically inert but are not readily available in the marine market.

Graphite Extruded Teflon – These products usually have the graphite lube physically extruded into the Teflon yarn before it is braided . Extruding the lubricant (graphite), mixed into the yarn, is a far superior process than “ impregnating ” the product after the extrusion & braiding process. This material offers the best heat transfer due to graphite’s inherent ability to transfer heat rapidly. The addition of graphite, as the performance lubrication, allows for minimal dripping and longer times between adjustments. The down side to graphite impregnated packing’s is that graphite is the most noble element on the galvanic scale. In other words graphite packing materials can cause localized damage to shafting and can increase anode erosion rates. The ABYC and Western Branch Metals (The largest prop shafting manufacturer in the US) specifically disallow the use of graphite packing materials. With the great performance come some cautions and risks.

This particular stuffing box is a 1 inch stuffing box and uses three rings 3/16 flax packing. These two surfaces, where the shaft and packing meet, tend to polish each other smooth, and if over tightened, can lead to premature shaft wear or excessive heat.

Over tightening of the packing-nut, and running the stuffing box with no water drips, will eventually wear a grove in the prop shaft and ruin it. It’s very important to allow a few drops of water per minute, when the shaft is spinning, for lubrication. Even the newer synthetic W.L. Gore GFO packing should have a drip or two per minute with the shaft spinning.

Empty Stuffing Box Nut

This is what the female stuffing box nut should look like, after you have removed all the old packing from it.

My Home Made Pick

I can’t remember where I found this pick, perhaps Sears, but it used to be straight and was designed for removing engine seals! I used a blow torch and a bench vice to create my own, custom made, flax removal tool and it works remarkably well. Even a sheet rock screw can be used to remove flax but in tight spaces it’s nice to have a couple of bends in your flax removal tool.

Getting Ready To Dig Out The Old Flax

In this photo I left about an inch between the male end of the stuffing box and the female nut. This is typical of the space you’ll have on many production boats.

WARNING: If you have not attempted this type of DIY job before it’s best to do it with the boat out of the water for obvious reasons. With the female flax nut removed water will flow into the boat from between the male end of the box and the shaft. Please be careful.

Grabbing The Flax

What you can’t see in this picture is the sharp end of my pick has been firmly embedded into the first flax ring and I’m ready to pull it out of the nut.

Removing Flax With a Pick

Success! The first ring of packing is on its way out..

Packing Nut Off & Old Packing Out

I don’t advise, and can’t with a good conscience, suggest the use of “miracle lubes” such as the moldable packing materials like the; “ West Marine Moldable Packing Kit “. While many have claimed good success with these miracle lubes others have not, including myself.

On a boat we had in 2000 I installed the “ West Marine Moldable Dripless Stuffing Kit ” and it eventually became a nightmare. The green stuff in the image is the “ moldable clay ” shown with the two rings of packing that came out of the female stuffing nut.

Article Edit: Since writing this article I’ve conducted extensive temperature testing of packing glands with a fixed temp probe mounted directly to a traditional bronze stuffing box. I have measured this now for over 6 years with various products. A digital temp display was mounted in the cockpit. What I have learned is that packing gland temperatures can be anything but static .

Why? What I discovered is that air can become entrapped in the shaft log and with no cooling water, meaning no drips, you can, quite suddenly and without warning, develop a massive temp spike. Some vessels are more prone to this than others. Our old Catalina 36 was quite prone to this issue. Even after converting to a PSS dripless seal, before they introduced the vent, I found that boat needed to be burped, due to entrapped air , multiple times per season.

At one point during testing we had motored for over 3 hours using a graphite impregnated packing set for less than a drip every three to four minutes. The temp stayed at steady at 85-102F for over three hours. We hit some prop wash from a large yacht and within 3-4 minutes the packing gland was pushing 300F. Ouch!  This same type of event happened about 14-16 times over a 6 month period using a very low drip rate. My goal in testing was to find the happy medium for the least-drips to the most consistently stable temps. I adjusted the gland for 1 drip per minute and the temp spikes were gone.

This is why stuffing boxes are intended to drip some. When they drip they also displace any entrapped air. Not all boats are prone to entrapped air in the shaft log, but many are. The simple act of backing down on an anchor can force air bubbles up into the shaft log and with no drip there’s no way for the air to escape.

It is my best guess that this is what happened with our “miracle clay” packing…

Packing Nut Showing Syntef & Teflon Flax

The idea behind this green moldable clay is that it will make your traditional stuffing box dripless . To install it you insert the first ring of flax, then pack in the green clay like substance and insert the second ring making, in essence, a green-stuff sandwich.

While the idea of a dripless shaft seal is not new this stuff, in my opinion, is probably not the ideal way to go dripless . Not only is it very, very tough to remove with a pick, and replace once installed, it also did not work as advertised for me. I would also note that since writing this article numerous readers have emailed me & reported similar overheating events.

What Happened?

Remember when I talked about air entrapment in a packing gland causing temp spikes, I suspect this was it. My suspicion is that the box became entrapped with air, the green-stuff then overheated by running totally dry. Running dry melted the green goo and it oozed out and completely plugged the male end of the stuffing box with a thick black sediment . This sediment now kept the stuffing box air entrapped and eventually a burning smell notified me to the problem in the bilge.

This black goo/sediment can only be described as, remnants of the green-goo lubricant . This gray/black goo totally plugged the stuffing box essentially preventing any cooling or lubricating water from getting to the female nut. If left alone for a long enough period it could have ruined the prop shaft or potentially started a fire or damaged the packing hose. When I went to inspect the burning smell I reached out to touch the stuffing box and blistered my finger tips with burns.

Again, many folks claim good success with the miracle-goo so take my advice as cautionary only and do your own research beyond what I’ve said.

Keep in mind that this box had been run in excess of 240 engine hours at the time of the melt down and this does not include the shaft rotation time for the prop free spinning while sailing . . Air entrapment is real, it can happen and does happen and if the box can’t drip, it can entrap air and  create problems. Even PSS seals are now plumbed to let air escape from the shaft log.

This Mess Of Green-Goo Really Messed Up This Stuffing Box

If you clicked on this picture to enlarge it you can see the black goo residue on the shaft caused by the green-goo moldable packing that had over heated and was clogging the stuffing box.

IMPORTANT: All traditional stuffing boxes require water for lubrication and this dripless-clay totally plugged the area between the shaft and the male end of the of the stuffing box as seen in the picture.

Even with the female nut totally removed, in the water, I was getting, at best, 4 drips per minute with the nut off! Please be cautious running any traditional stuffing box dripless.

Dripless Vs. Drip-Less

Once again the sleazy marketing mavens have muddied the waters and done their best to mislead the average boater.

Dripless = A stuffing box that has zero drips

Drip-Less = A stuffing box that drip s less but still needs to drip some

Dripless is a term that is best forgotten in regards to standard traditional stuffing boxes. The proper term is drip-less or a box that will drip less often.

The green-goo stuffing box actually got so hot, from the lack of water lubrication, that it started to smell and I burned & blistered my fingers when checking on it. This is what eventually can happen when you opt for dripless vs. drips less.

Keep in mind this did not happen instantaneously and took approx 240 hours of run time to accumulate enough Syntef/Clay gunk to clog the stuffing box. It ran at what I thought were normal temps during and after break in as I measured it with an infrared thermometer.

I now know that spot temp checks do not tell the whole story . Temp spikes and excessive heat are likely what caused this stuff to clog my shaft log over time. In my opinion this stuff is not suitable for a “tight” shaft log where you don’t have sufficient clearance between the shaft and the male end of the stuffing box.

How does air get in there? Docking or anchoring with quick blasts of reverse can send  air bubbles up into the shaft log. Sailing in rough weather can also lead to air entrapment. If the shaft log is totally sealed or “ dripless ” the air accumulates until the box has no lubrication.

There is a good reason traditional style stuffing boxes are meant to drip. These newer packing materials should not be considered “ dripless ” and should be consider to drip less often .

Beyond entrapped air causing lubrication issues, stagnant water in the shaft log can lead to crevice corrosion of a stainless alloy prop shaft, as you’ll see below.

Why It Should Drip Some

Real Tobin Bronze shafting has been long gone for many years now, and as such, alloys in the stainless family, such as Aqumet & Nitronic are now being used it its place. These alloys, like type 304 and 316 SS, can suffer from a phenomenon called crevice corrosion.

Crevice corrosion is worst when a stainless alloy is in contact with seawater, and also oxygen starved . Crevice corrosion can also happen to bolts between wet or leaking decks, chain plates, or in stainless keel bolts where they pass through the keel stub. Most folks are aware of chain plate and keel bolt corrosion but are often unaware that it can also happen to stainless alloy prop shafts. Allowing a packing box to drip helps to keep the water in the shaft log from becoming oxygen depleted .

Over the last 10-15 years there has been a startling rise in crevice corrosion of prop shafting. With the newer packing materials, and misleading advertising, that use phrases like drip-less, the problems have only continue to escalate . The unclear marketing has caused DIY’s & professionals alike to think it means “ dripless ” not drips less . In light of this muddy marketing owners have been starving the packing box area of oxygen by not allowing any fresh oxygenated water to pass through it.

Going full dripless can potentially lead to the destruction of your prop shafting from the effects of crevice corrosion. While some packing materials such as Gore GFO, Ultra-X or GTU may be able to be adjusted to be mostly dry, and still some what cool to the touch, it’s still a poor idea from a crevice corrosion stand point.

Another pit fall, when a stuffing box is run totally sealed and “ dripless “, is that they can trap air up in the shaft log. All it takes is a quick blast of reverse, and the resulting bubbles forced up and in. Sailing in rough weather can also lead to entrapped air in the shaft log. Once enough air becomes trapped up in the shaft log the packing box, you thought was cool to the touch, begins cooking while you least expect it.

If a stuffing box is allowed to drip, even at a slow rate , it allows for excellent cooling, longer shaft life, less opportunity for crevice corrosion and less opportunity for trapped air to run the box in a totally dry state and cook it.

0.05″ Of Shaft Wear

This shaft had roughly 0.05″ of stuffing box wear and was deemed scrap metal by the shafting shop. This owner was using a Teflon impregnated natural flax and thought when the advertising said “ drip-less ” that it meant it was supposed to be “ dripless “. This was an expensive mistake you should aim to not repeat.

New & Old Packing

This photo shows the old packing with the “miracle clay” and the new GTU packing. GTU is a knock off of Gore GFO, but it frays worse due to the poorer braid design.

The Gore is the one of the best of the flax type packing materials in terms of heat dissipation but it is at the very, very top of the galvanic scale, which can cause other issues.

These packing materials also need a few drips per minute to run cool and not damage the shaft. My one complaint with this GTU packing, made by Western Pacific Trading and sold through West Marine, is that it tends to fray easily and does not make the cleanest cuts even when using a brand new razor blade.

Scrap Tubing As A Cutting Jig

Many sail boats have a 1 1/4″, 1 1/8″, 1″ or 7/8″ inch prop shaft and a piece of scrap dodger tube, in your shaft size , works great as a cutting jig for new packing rings.

Use a set of calipers to make sure your “jig” of choice is the same O.D. as your prop shaft and then cut away. I usually cut the rings in this manner but you could also cut them on the actual prop shaft too.

Please cut the rings on the outside of the boat where the shaft exits the hull between the strut and the hull and not at the stuffing box. If you cut the rings on the shaft, at the stuffing box, you run the risk of scoring the shaft and causing a burr that can damage the new packing and inevitably leak more until the burr gets polished away from the friction. This could take a very long time unless you are in heavily silt laden water…

Cutting New Rings – Sub-Optimal

This may get a little confusing but there actually is a optimal way and a sub-optimal way to cut your packing rings.

In this photo I am holding my razor blade at a 45 degree angle parallel to the shaft. Unfortunately if I cut the rings in this manner they do not seal quite as well. Yes, it will work but it is not optimal . Because the shaft nut does not compress the flax on the circumference, like the action created by a hose clamp, cutting it 45 degrees & parallel creates a less than optimal seal .

Cutting New Rings – Optimal Method

In this picture it’s easier to see the 45 degree cut and how the two ends of the packing will join together. The packing nut will actually compress these two ends together and create a better butt-joint than if they were cut vertically for a circumference (think hose clamp) type compression. I told you this was a little confusing.

Once the ring is cut be very, very careful to minimize fraying before installing it. If you’re using impregnated PTFE or traditional flax packing fraying is usually not an issue. With GTU or Gore GFO etc. fraying can be an issue.

IMPORTANT: When you cut rings this way they will  not wind up the correct length. Cut it and then shave one end down until you get the correct fit over the shaft where the two ends butt perfectly. A perfect fit is with the rings neither being too large, so as to cause a gap with the ends butted, or too small so the ends won’t quite butt together..

Here’s Why

This is a good illustration of why the cut should be made the way I have shown above. The compression of the packing nut seals the butted ends together nearly perfectly. Little details like this make for an easily adjusted stuffing box with a correct drip to temp ratio.

Three Packing Rings Installed

This photo shows three rings installed. This packing nut fits three rings, some don’t and it’s not a huge deal if one does not fit more than two rings. Three rings is preferred and considered optimal. You can also go to four but beyond that cooling issues can happen.

Thread engagement is critical and my personal preference is for four full thread peaks of engagement between the female nut and male stuffing box threads. This is four thread peaks with three rings installed and seated.

Old Teflon RIngs & Syntef Shown With GTU Rings

Here are two of the new GTU rings and the old stuff. Note the fraying I discussed earlier even though I tried to minimize it. I have discovered that Western Pacific Tradings GTU frays considerably more than Gore GFO or Duramx Ultra-X. GFO and Ultra-X barely fray at all when cut. This is due to the braiding process used.

Perhaps, to prevent fraying with GTU, you could heat up a little wax in a bowl and as soon as you cut the ring dip the ends in the wax like whipping a line. There is actually a fair amount man-handling, of the rings, between the time when they are cut and inserted and some measure of fray prevention should be attempted when using Western Pacific Trading GTU or just use GFO or Ultra-X.

Different Braider

The product I used above for this article was Western Pacific Trading GTU from West Marine. Initially I thought it was some Gore GFO I had lying around but GFO has the words “ GFO ” embossed right on the packing and after going through the photos carefully I could not find the silk screened GFO logo.

I had never had Gore’s GFO fray but the GTU product does. The photo to the left is Duramax Ultra-X which has a very similar construction, and braid, to Gore’s GFO. It does not fray when cut like GTU does.

Johnson-Duramax Ultra-X can be purchased by the foot from Hamilton Maine and it cuts cleanly.

Duramax Ultra-X Cuts Cleanly

Here’s an image of a 45 degree cut. This one comes up a bit on the short side so be careful in your cutting.

This ring was cut from Duramax Ultra-X. It is important to keep in mind that these graphite impregnated/extruded packing materials can dull a razor blade quickly so rotate in a new blade if the old one is cutting poorly. Razor blades are cheap.

Start With Your Cut Rings Ready

One of the last things you want to do, if changing your packing in the water, is to cut your rings during the project. Please do yourself a favor and pre-cut your rings.

If you’re new at this I would recommend starting with 4-5 rings as you may damage one or two in the installation process.

Edit and Answers:

I’ve received far too many emails asking what this packing material is to ignore them, so here are the details.

This is the packing material I now use. It has been in the development and testing stages since 2013. Unfortunately it is not yet on the market and is still in the testing stages. As a marine electrician and corrosion specialist I have all but stopped using the graphite impregnated packing materials I used when I initially wrote this article back in the early 2000’s. They perform quite well, but as I discovered, can lead to a host of other issues most notably, galvanic incompatibility issues. I discuss this further down in this article.

This high performance non-graphite packing, SynBraid®, is a 100% galvanically inert synthetic high performance packing, not a “PTFE infused” product with acrylic or flax yarns making up the braid. The SynBraid® yarns are actually extruded with the proprietary lubricant in the yarn not “infused” after the yarns are extruded. I expect SynBraid® to be on the market sometime in early 2018.

Mark The Nut Where Your Seams Are

When doing this in a boat it is a very good idea to mark the exterior of the nut where each seam is so you can stagger them. Use a packing tool like I show below to compress them into the nut. Only when all rings are in the nut can you then tighten it.

Tightening the nut to seat the packing, especially with the newer more slippery packing braids, can move the seam and you’ll now be blind as to where your seams are and will need a dental mirror to confirm seal position.

You will be best to make yourself a packing seating tool.

New Packing Rings

This is the last step. In this picture I have two of the three rings wrapped around the shaft in a stepped and alternated order.

NOTE: Please ignore the fraying . This was not a real boat and in the process of photographing this I man handled the rings far more than you would. The butt ends of the rings should not look like this.

You’ll want to offset the rings butt-joints 1/3, 1/3, 1/3 for a three ring box or 1/2 & 1/2 or said another way 12 o’clock and 6 o’clock for a two-ring box.

It’s also perfectly fine to wrap one ring at a time and push the nut over it, but without turning it, until you get all three rings into the nut and staggered. It’s best when using this method of stuffing the rings to mark the outside of the nut with a Sharpie marker where the joints are and then when all rings are in the nut, and staggered, you can finally thread the female nut onto the male part of the box.

I custom made my own tool for this & it has a similar thickness to the flax for stuffing the nut (see the tool below). I don’t advise the use of a pick to stuff the flax into the nut as this can cause significant unlaying or twisting of the flax especially with GTU. When ever possible try to get at least three rings of packing in your stuffing box as most are designed for at least three. Some nuts can actually fit four & if so go for it but make sure you still have enough exposed threads to get sufficient thread engagement for the female nut.

IMPORTANT: You really need to use the correct size packing or else you will either have overheating or leaking issues.. Going one size to0 big can eventually wear a groove in the shaft and one size too small will never seal properly. Please use due diligence to determine the proper packing size for your particular stuffing box.

The Home Made Packing Insertion Tool

Many folks have asked me how I insert the packing rings into the female nut. Well, like anything dealing with boating, it’s not always easy but can be done with a little Yankee ingenuity.

I decided that in order to keep my ring joints staggered, and to get them properly seated, I needed a new tool. I wanted a tool that was to be perfectly parallel with the prop shaft when inserting and seating the flax but that did not involve twisting the nut or threading it onto the male end . .

You need to seat the packing without causing any twisting and there were no commercially available tools to do this, so I made one. Using a screw driver will not give you the correct angle to seat the flax properly and could potentially mess up the joints or put twists in the flax rings. Seating the packing with no twists is important.

Insertion Tool Clipped On Shaft

Making this tool took less than five minutes but can really save time and headaches. To build this device I decided to use a short piece of 1-1/4 inch PVC pipe with about 1/3 of it cut out so it would fit over a 1″ shaft.

I left just enough material so it could clip itself onto the shaft and stay in place without any hand holding.

For this process I cut the 1-1/4 inch PVC pipe to 2-1/2 inches long. I then inserted this 2-1/2 inch piece into my bench vise and used a hack saw to make two more cuts. These cuts removed just enough of the 1-1/4 inch PVC to create the device.

You’re probably wondering why I used 1 1/4 inch PVC if I had a 1 inch prop shaft? Well.. I used it because it’s all I had on hand and I also own a heat gun so it was very easy to heat the PVC and wrap it around a piece of scrap 1 inch dodger tubing for a perfect heat formed fit. If you don’t own a heat gun dropping PVC into boiling water will soften it enough to mold it to the shaft.  Once it cools down it will simply click into place .

Seating The Flax

This photo shows the female nut sliding over the packing insertion tool and seating the packing rings . The tool works very well and unfortunately no one actually makes one. Hey, I bet West Marine could sell one for $85.00… ( grin )

GFO, GTU & Ultra-X Warning

WARNING : While I do like the performance of graphite impregnated packing materials such as Duramax Ultra-X, Gore GFO or Western Pacific Tradings GTU they can be potentially dangerous to underwater metals. I have used it on my own vessel but inspect the Aqualoy 22 prop shaft yearly .

“RC, Why the warning then.?”

It’s all about corrosion. Graphite is the most noble element on the galvanic scale.. As such anything in the drive train becomes anodic or sacrifices itself to the packing. Older bronze shafts, really more of a brass because they had high zinc content, can be damaged by these new high tech graphite impregnated packing materials.

The damage shown in this photo happened in one season and with intact prop shaft anodes . The shaft was in perfectly fine condition when packed, and a year later this is what it looked like.

The packing used on this shaft was Gore GFO a graphite impregnated packing. If you have a bronze shaft please use extreme caution with graphite impregnated packing materials.

I don’t tend to see these issues with Aqualoy 22 shafting but I have seen it with bronze and lower grades of stainless. Please use these packing materials carefully. If you choose them please do check on the shaft periodically.

Also, please be aware that after you install a graphite impregnated packing you will see some accelerated anode erosion rates. No dire need to be alarmed at this  but do keep up with them and check them more often until you are familiar with the new erosion rate..

Here is where the ABYC Standards come down on graphite packing :

ABYC P-6: “6.7.4 Graphite impregnated packing material shall not be used because of the possibility of galvanic incompatibility with the shaft material.”

I suspect what we are seeing in this photo is exactly the “ galvanic incompatibility ” the ABYC warns against.

We now know where the ABYC stands on graphite packing but what about the largest prop shaft manufacturer in the United States, and possibly the world, Western Branch Metals?

Western Branch Metals: “ Do not use graphite packing in the stuffing box . Instead, use a packing material that causes the least abrasion after the lubricant wears away. The use of graphite-impregnated packing is not recommended because of the possibility of galvanic corrosion of the shaft material.”

Now we have not only the ABYC but one of the largest prop shafting manufacturers on the planet both saying exactly the same thing. Do not use graphite packing’s. As they say your boat, your choice.

With all that said there are still many happy boaters who have had decent results with these graphite packing’s. Please remember however that they should not be treated as a set it and forget it packing. If using these graphite impregnated packing materials I would strongly suggest checking the shaft at least yearly .

Here’s the finished product after installing three new rings of packing material.

When initially installing the rings of packing lightly tighten the nut just until you start to feel some resistance then stop. DO NOT OVER TIGHTEN THE NUT . The final adjustment will be made after running the motor and shaft for a while.

Setting The Drip Rate

Proper adjustment for GFO, GTU or Ultra-X is up to a few drops per minute when the shaft is spinning. You’ll ideally want it adjusted for nothing more than slightly different from the sea or lake water temp, about a 15 – 20 degree differential, or slightly warmer to the touch. Measure these temps after the shaft has spun for a while.

Adjustments should be made in either half a nut-flat or “one nut-flat” (of the nut) at a time. Adjust in small increments only and not more than one full flat of the nut at a time.

W.L. Gore recommends not adjusting the stuffing box until you have run the boat in gear for about two hours of time. This allows the packing to take a set and break in some.

When adjusting other types of flax the stuffing box should be relatively cool/warmish to luke warm, at most. With traditional flax packing it should drip and must drip while the shaft is spinning.

The cooler your stuffing box runs, the longer shaft life you’ll have. With GFO they claim temps up to the 125-130F range are technically safe for the packing. In my opinion & experience monitoring stuffing box temps over a 6+ year period, 125F – 130F generally means there is not enough cooling flow through the box.

Any entrapped air, with normal temps this high, can cause a big spike in box temp. Aim for 15-20 degrees warmer than the ocean or lake temp but a little higher, with GFO, GTU or Ultra-X, should not kill the deal .

Some boxes will even drip when the shaft is not spinning and this can be entirely normal depending on the condition of your shaft. Do not get stressed if you can not make it drip free at rest as not all shafts are in good enough condition for this to always be the case. Ideally they should be but many are not.

Please do not get in the habit of tightening the stuffing box when leaving the boat . Natural flax based packing’s are not elastic and do have a memory, in a sense, and they will not necessarily return to their uncompressed state . Doing this will severely shorten the life of your packing and it will start leaking, continuously, in short order.

I generally don’t like rules-of-thumb for drip rates and really hesitated to even put one on here. My reason for this is that every shaft has differing levels of wear and thus the drip rates are usually slightly different in every installation.

The best rule of thumb I’ve found over the years is this:

Aim for the least amount of drips when the shaft is spinning but before the box develops any heat rise beyond 15-20F, beyond sea or lake temps.

Again, it’s a drip to heat ratio not necessarily just a drip ratio. Little to no heat is the most desirable. Traditional flax packing can drip as little as about 5-10 drops a minute, if adjusted correctly, while running, and this drip rate allows lubrication of the shaft.

Do not make any adjustments to the packing nut, with traditional flax, for at least 24 to 48 hours after launching as the plant based flax packing will absorb moisture and swell. This swelling can cause overheating of the stuffing box, if it’s adjusted too quickly after launch.

Premature tightening of traditional flax packing can result in potential problems. A good and safe practice is to adjust the packing by half-a-flat turns after two hours of use or until you have your drip to heat ratio correct. You can actually use an infrared thermometer, often called a pyrometer, to make this adjustment process easier but usually your hand will suffice as a good gauge.

If you want a totally dry bilge then a dripless type seal such as a PSS or Las-Drop is the way to go. I’ve provided full installation instructions for that type of seal too in another article.

Good luck & happy boating!

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One comment.

I was used to using flax packing and adding a ring every year or few. An old diesel mechanic told me that he never removes the old packing, just adds a new ring. So when I switched to Gore-GFO, I didn’t realize that it would not wear away like the flax did. So every few years I added another ring until no more would fit. Deciding to remove all the old, I was surprised to find all of the rings, maybe 6 in all, intact with no disintegration. However, I found my bronze shaft had suffered some wear, probably due to over tightening. Word to the wise: When using these newer packings, tighten only enough to just stop the drip when not running, yet allowing a slow drip when shaft is turning.

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Stuffing box inspection and replacement

The stuffing box is a critical part of the boat. It allows a driveshaft to spin through the hull without allowing water to pour into the vessel. These units are often deep down in the boat, behind the engine and with limited access. On many sailboats it is often under the cockpit with side access through a locker — a dark and damp place often forgotten about until the bilge pump kicks on every few minutes and one wonders where the water might be coming from.

After removing all that resides in that locker, crawling inside and removing the small access panel — perhaps head first — the stuffing box becomes visible. Maybe it has been a few years since your last visit, but did you remember to bring two large stuffing box wrenches and a flashlight? To adjust the traditional stuffing box, you need two wrenches in order to loosen the backing nut off the cap nut. This requires two hands in this small space as well as being able to see what you are doing while breaking the nuts free. These nuts are tight and some two-handed muscle is required to free the nuts from their grip on each other. Proper wrenches are key; the adjustable stuffing box wrench might work for you, but a proper toolbox should include a set of fitted stuffing box wrenches to avoid a lot of pain and frustration.

If you succeed here, the job of adjusting the stuffing box is fairly straightforward: Tighten up the cap nut until the water stops gushing in, then retighten the two nuts together. More often than not, these nuts are corroded and, without proper tools and leverage, a tough nut to crack.

Now it’s time to crawl out of the locker, start the engine, put her in gear and re-enter that locker (don’t forget your flashlight) to see how the adjustment holds up in motion.

The stuffing box should drip ever so slightly now, say a drop every five to 10 seconds. No drip is no good because without a little bit of water lubrication, the shaft will heat up and wear over time, creating a groove in the shaft that no amount of packing can stop anymore. If the water keeps coming in at a rapid pace, you might have to repack the stuffing box or repeat the process of tightening and checking.

Don’t adjust the stuffing box while running the engine in gear! Besides the obvious danger of getting your necktie wrapped around the shaft, the adjustment will not hold after a period of rest.

On larger sailboats and trawlers, the access to the stuffing box or boxes might not be a problem and adjustments can be made while sitting down and with good light. In these cases, the traditional stuffing box is a simple, well-proven maintenance item. However, if the stuffing box is as hard to reach as described above, a dripless stuffing box might be the solution.

The dripless stuffing box does what its name suggests, leaving you with a dry bilge and, more importantly, with a low-maintenance stuffing box. No big nuts to adjust in tight spaces with big tools, no packing to replace with tweezers in this dark corner of the boat while hanging upside down in a rough sea.

The expense of refitting a dripless stuffing box is well worth it if it is installed by the boatyard, but with the proper tools, this job can be done by the handy boatowner as well.

Start by removing the prop outside the boat and the set screws in the shaft coupler inside the boat. The goal is to pull the shaft out of the coupler far enough to remove the old stuffing box off the shaft log. A shaft puller is the ideal specialty tool for this job — the dead weight of the slider jars the shaft out of the coupler in a few minutes. With the shaft pulled out of the coupler, the old stuffing box can now be removed and the shaft and shaft log can be examined.

To order a new stuffing box, the shaft size and shaft log’s outer diameter need to be measured. For example, in this case it is a 1-inch shaft and a 1.75-inch shaft log. Clean and wet sand the shaft on the surface that will receive the new stuffing box and examine it for burrs and grooves. If the shaft shows severe grooves from an overheated stuffing box as described above, there is a chance that the new stuffing box will leak (more on that later), or maybe a new shaft is needed after all. The new stuffing box by PSS comes with three key components: a nitrate bellows, a stuffing box with carbon graphite flange and a stainless steel rotor. The rotor will be attached to the shaft and turn on the graphite flange to create a watertight seal by compressing the bellows with the rotor. The polishing of this stainless steel rotor on the graphite flange with the water nearby makes for a virtually maintenance-free seal.

Install the bellows onto the shaft log and tighten the hoseclamps. The 3/8-inch nipple will point up. Connect a piece of 3/8-inch marine-grade fuel line to it, double-clamped, and run it 2 feet above the waterline. Secure this hose along the way — if it were to fall into the bilge, this vent hose would become a fill hose.

Take the rotor and pre-position a set screw in each of the two holes with a drop of thread lock. Position the shaft so the stainless steel rotor can be installed onto the shaft. This is the tricky part because the rotor has two rubber O-rings inside it that must not get damaged during this installation. That’s why wet sanding the shaft is so important. Use soapy water — not grease or penetrating oils — to slide the rotor onto the shaft. Lock the shaft into position, as it will want to walk out while you are trying to push the rotor on. Use lots of soapy water and move the rotor at least an inch past the keyway of the shaft. Prepare the key and keyway, and reinstall the shaft into the coupler. Careful tapping will position the shaft and line the key up properly.

 The shaft puller can now be used in reverse to re-install the shaft into the coupler to its old marks. The set screws can be wrenched down and seizing wire should be added. The prop can also be reinstalled. Now, the final touch on the stuffing box: The stainless steel rotor needs to be slid down the shaft to press upon the carbon graphite flange. The rotor will compress the bellows, but how much will depend on the size of the shaft. In this case, three-quarters of an inch of compression is needed for a 1-inch shaft. Mark the shaft at the point of touching just the flange, slide the rotor another three-quarters of an inch onto the shaft and tighten the set screws down. Here is the part were those old grooves on the shaft can be a problem. Test that last three-quarters of an inch and see if the groove is interfering with the rotor. Moving the bellows up or down the shaft log can relocate the final position of the rotor on the shaft. If all looks good, add the second set of set screws with thread lock glue on them as well.

When the boat is launched and commissioned, inspect and run the engine in gear and observe. The rotor and the graphite will make a perfect seal almost immediately, but a little spray might occur occasionally. It should stop after a minute — if not, a bit more compression might be needed. A poor engine alignment can cause the shaft to shake a lot and make the dripless stuffing box drip.

The stuffing box is now a lower-maintenance item and can be quickly inspected and cleaned with one hand, even if upside down in that locker.

By Ocean Navigator

Stuffing Box Maintenance

By Morgan Williams

The stuffing box is the seal around a boat’s propeller shaft that keeps the water out and allows the shaft to rotate freely. Ninety percent of all sailboats with auxiliary inboard engines have a flexible stuffing box with traditional packing gland that usually goes unattended until it begins to leak, usually at the worst possible time.

The traditional stuffing box consists of stern tube which is slightly larger than the prop shaft. A gland nut or packing nut threads onto the stern tube. Inside the gland nut is the packing, which creates the seal. The packing is wrapped around the shaft and inserted into the gland nut. As the gland nut is tightened onto the stern tube, the packing is compressed against the shaft, creating a seal. Lubricating the seal requires that when the shaft turns, two to three drops of water per minute drips out of the stuffing box. There is also a locking nut on the stuffing box that locks the gland nut into position.

There are three basic types of stuffing boxes. The rigid stuffing box is mostly used in powerboat applications. The flexible stuffing box is found in most sailboats, and the relatively new flexible shaft seals are used in both sail and powerboats. In a rigid stuffing box, the shaft comes through the stern tube where the stuffing box is bolted to the tube or hull and is affixed or part of the boat. In these applications, alignment of the shaft to the stern tube is critical for proper operation.

Check your boat’s stuffing box immediately after launching,and regularly throughout the season. Note the correct installation of the hose clamps on this flexible stuffing box.

In a flexible stuffing box, the stuffing box is connected to the stern tube with a short hose and four hose clamps – two on the stuffing box side and two on the stern tube side – that hold the assembly together. The hose is usually a four-ply steam hose, which is very strong and durable.

Shaft seals do the same thing as a flexible stuffing box, but without the packing seal. The seals have a bellows hose which is clamped to the stern tube. On the end of the bellows is a carbon/graphite flange. At the engine end of the shaft there is a stainless steel rotor which mates with the carbon/graphite flange. The stainless rotor is pressed against the flange, compressing the bellows and creating a seal between the flange and rotor. When the shaft turns, the carbon flange is fixed and the stainless rotor spins with the shaft. The graphite provides lubricant and a thin layer of water provides the seal for the shaft. Most shaft seals have a nipple for a vent hose to ensure that the stern tube remains full of water for cooling the carbon/graphite flange. On high-speed applications, the vent tube is connected to the raw water side of the engine, so seawater can be injected into the stern tube for cooling.

As with all jobs, disassembling a stuffing box is easier if you have the right tool, and the best tool for the job is the Ridgid E-110 wrench (you’ll need two).

There are three basic types of stuffing box packing: flax packing, Teflon packing, and graphite packing.

Flax packing has been around for 100 years. This greasebased packing can last for years and is very reliable. The one drawback to flax packing is that if the stuffing box gland nut is overtightened, flax packing can heat up in the gland nut, which causes dangerous temperatures and scoring of the shaft. So, when adjusting a stuffing box with flax packing, hand tighten the nut, adjusting it to reach the two to three drops per minute rule.

Teflon packing is great to use, and can last longer than flax packing. But this white material is hard to cut properly and requires a fresh razor blade. It’s also tricky to adjust the packing gland to get two to three drips a minute, and a number of adjustments may be needed to get it right.

Graphite packing is excellent because it’s a lubricant, which reduces the chance of burning the shaft. There are two drawbacks with graphite packing. It is very expensive and it can promote corrosion because graphite is high on the galvanic table, although I have been using it for years without an issue.

This “cutaway” photo, courtesy of the Chesapeake Bay Alberg 30 One-Design Association, shows the orientation of parts inside a flexible stuffing box. © alberg30.org

Repacking a stuffing box is a simple task. You’ll need two adjustable wrenches or two pipe wrenches. The tool that works the best is the Ridgid E-110 wrench. You must grab the gland nut and locking nut in opposing directions, to reduce the torque on the stuffing box hose. Once you have broken the lock nut and the gland nut free, spin the gland nut off the stuffing box towards the transmission. Now the fun really begins: removing the old packing. The best tool to use is the corkscrew-like tool available at any ship’s store. You screw the tool into the packing inside the gland nut and pull out the old packing.

To make properly sized rings of flax packing, wrap a length tightly around the prop shaft and cut across the rings with a sharp razor blade.

Now it’s time to size up the new packing. Packing comes in various sizes, with 3/16 inch and ¼ inch the most popular sizes for shafts in the one-inch range. It is very important to match the size of the packing to the opening in the gland nut. To cut the packing to length, wrap a length of packing around the shaft five times and pull it tight around the shaft. Using a sharp razor blade, cut across the rings with a diagonal cut. You now have four or five sized rings of packing. Now, insert the packing rings into the packing nut, offsetting the joints of packing from one wrap to another by 120 degrees. Generally, three to four rings will fit inside the nut.

Once the packing is in the gland nut, tighten the gland nut on to the stuffing box. I usually hand tighten the gland nut and then give it ¼ turn with a wrench, and then lock the nut to the gland nut. I make final adjustments after the boat is launched. As soon as your boat is launched, check the stuffing box. If it is leaking before you start the engine, it needs to be tightened up. Only tighten the nuts one quarter turn at a time. When the water stops dripping, start the engine and put the transmission into gear for a few minutes. Then shut down the engine and feel the stuffing box. If it is hot, the packing gland is too tight. Adjust the gland, restart the engine and recheck the stuffing box. Some warmth is okay in the beginning while the packing sets in. Remember to watch for the two to three drops a minute coming from the stuffing box while the shaft is turning.

Rings of flax packing should be inserted into the packing nut with the cuts offset by 120 degrees from one ring to the next.

While working on a stuffing box, it’s also a good time to inspect the hose clamps for corrosion and wear. Take a look at the hose for cracking or softness, indicating it’s time to replace it.

Happy motoring.

Morgan Williams operates Holmes Marine Services Inc., a full service mobile marine business specializing in sailboat repairs including diesel engines, electrical and charging systems, steering and propulsion. Morgan can be reached at 203-395-1051 or HolmesMarine@sbcglobal.net

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Service Your Stuffing Box

• By Steve D Antonio
• Updated: December 4, 2008

prop shaft and packing nut 368

When properly installed and adjusted, a stuffing box will provide hundreds, if not thousands, of hours of reliable, nearly leak-free service.

The keys to a stuffing box’s longevity are twofold. The first and most common cause of chronically leaky stuffing boxes involves the condition of the surface of the propeller shaft directly beneath the packing. If it’s in any way irregular, pitted, or damaged, the packing will be torn up each time the shaft rotates beneath it, which may be as many as 1,500 or 2,000 times per minute. The pitting or damage is often caused by the stuffing box’s oxygen-poor environment. If this is the case, then no amount of repacking-regardless of the type of space-age “leak-proof” material you use-or adjustment will resolve the problem. Two solutions exist: Replace the shaft, or use a longer or shorter stuffing-box hose to move the location of the packing over an undamaged section of shaft.

The second problem, which also results in chronic leakiness, is often caused by a sailor’s response to the first problem: overtightening the nut that contains the flax packing. When the nut is overtightened, the flax overheats, and the wax lubricant melts and runs out. Green or black sticky material under the box means that the stuffing box has overheated; the box must now be disassembled. Clean out all vestiges of packing and wax, then clean the shaft and lightly polish it using 400-grit emery cloth.

Overtightening the packing nut so that the stuffing box drips no water at all can wear a groove in the prop shaft and ruin it. When the shaft is spinning, the stuffing box must allow a few drops of water per minute for lubrication. A variety of formulas exist to establish the number of times a stuffing box should drip while the shaft is spinning. Forget ’em. As long as the box isn’t dripping too much and isn’t running too hot, then all is well. Some boxes, particularly those used on sailboats, need not drip at all to meet this criterion as long as the packing remains moist. Take the box’s temperature after running at cruising speed for half an hour or so; it shouldn’t be more than 20 degrees F above the ambient water temperature. If you use an infrared pyrometer, you can carry out this test while under way. If you use a contact thermometer or your hand (too hot to touch is usually between 130 F and 150 F), shift into neutral, then check the temperature right away.

After repacking the stuffing box, use two wrenches to jam the locking nut against the adjustable packing nut. Never use a single wrench for this procedure because you’ll run the risk of spinning the nut off. More wraps, by the way, aren’t better where stuffing-box packing is concerned. Most boxes work very well with just three rings of packing; place the seams or joints at angles of 120 degrees to each other. Using too many wraps causes the shaft and box to overheat, which leads to packing failure as well as to galling of the shaft.

Finally, carefully inspect the stuffing-box hose and clamps at least once every sailing season. Use only all-stainless-steel, non-perforated hose clamps; avoid using T-bolt clamps because they’re prone to crevice corrosion in this application. Replace hoses at the first sign of fatigue, every five years, or whenever the shaft is removed, whichever comes first.

Steve D’Antonio, a regular CW contributor, offers services for vessel owners, boatbuilders, and others in the marine industry through Steve D’Antonio Marine Consulting. Next month, he writes about prop-shaft alignment.

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It's normal for a traditional stuffing box to have a slight drip when properly maintained, but in this case for a 1978 Catalina 30, lack of maintenance led to a seal failure and rapid water intake.

Sometimes as a sailor you are learning to run before you can walk or even crawl. If the auto bilge pump isn’t working, maybe it’s faulty wiring or is it clogged? The seawater pump slowly drips and that leads you down a road of a possible impeller repair. And sometimes as a sailor it takes almost sinking to learn one important message “Check your stuffing box!” Wait. Let me rephrase this “LEARN what and where your stuffing box is!”

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Well that sounds like a harrowing experience. Good old dad to the rescue. 🙂 We sail the same waters. Always comforting seeing many SeaTow and TowBoat US vessels in the area.

It’s my understanding that with a dripless shaft seal, you don’t have a traditional stuffing box anymore. Seal and connections still need to be checked, but there’s no flax, or need to burp the seal for proper lubrication with a dripless. At least that’s what they told me, as I have a Tides Marine dripless that recently needed replacing.

Thanks Brian for your comments! Nice to see you also sail the same waters too. I am also under the same impression with the dripless. I don’t think anything is truly maintenance free but just a different configuration that requires differing types of checks. So far ours has been okay, but then again you never know 😀. Sail on!

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Black box recovered from superyacht wreckage breaks down painful timeline of sinking

The poignant final 16 minutes onboard the tragic Bayesian yacht have been revealed as the boat’s black-box data has been analysed by police probing the disaster.

• 15:03, 24 AUG 2024
• Updated 15:12, 24 AUG 2024

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A black box recovered from the Bayesian superyacht breaks down exactly how it sank in a painful minute-by-minute timeline - after divers retrieved the body of British teen Hannah Lynch

The poignant final 16 minutes onboard the vessel have been revealed as the boat’s black-box data has been analysed by police probing the disaster. The information recovered from the Bayesian's Automatic Identification System (AIS) breaks down exactly how it sank in a painful quarter-of-an-hour timeline.

It comes as divers recovered the body of the final missing passenger from the wreck - British teenager Hannah Lynch - daughter of tycoon Mike Lynch, who was retrieved on Thursday.

An AIS tracking system sends information from onboard boats to coastal stations, alerting officials to movement and distress. As part of a probe into just how the luxury 184ft superyacht toppled and plunged to the bottom of the sea, killing at least six people, cops are analysing the data.

It shows that at 3.50am on Monday the Bayesian began to shake "dangerously" during a fierce storm, Italian outlet Corriere reports. Just minutes later at 3.59am the boat's anchor gave way, with a source saying the data showed there was "no anchor left to hold".

After the ferocious weather ripped away the boat's mooring it was dragged some 358 metres through the water. By 4am it had started to take on water and was plunged into a blackout, indicating that the waves had reached its generator or even engine room. At 4.05am the Bayesian fully disappeared underneath the waves.

An emergency GPS signal was finally emitted at 4.06am to the coastguard station in Bari, a city nearby, alerting them that the vessel had sunk. Survivors and witnesses from a small nearby boat - along with official reports - initially helped piece together an account of how the disaster unfolded on Monday morning.

People reported seeing a "tornado" - later clarified as a swirling cloud of air known as a waterspout - hit the 246ft tall mast. Officials have confirmed that this is what toppled the boat, causing it to capsize and take on water before it sank to the bottom of the sea.

Early reports suggested the disaster struck around 5am local time off the coast of Porticello Harbour in Palermo, Sicily. The new data pulled from the boat's AIS appears to suggest it happened an hour earlier at around 4am.

Top news stories today

Some 15 of the 22 onboard were rescued, 11 of them scrambling onto an inflatable life raft that sprung up on the deck. More details about the disaster surfaced yesterday as emergency workers revealed how the passengers tried to flee the water as it gushed onboard.

Divers said the guests pulled from the wreckage fled their cabins on the right - or starboard - side of the boat and tried to "climb" to safety by heading for the left - port side - where they were found.

A source working in the investigation told Italian outlet Courier: "We found them all on that side. We had maps with the layout of the cabins and the positions of the guests, and that's not where we recovered them."

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Drugs trial hears £1m of cash found in house

A drugs trial has been told that police discovered more than a million pounds in cash during the search of a house in Glasgow.

Most of the money was in heat-sealed plastic packages inside four Lidl supermarket bags.

The discovery was revealed during the trial of six men allegedly involved in a worldwide drug trafficking operation.

Prosecutors at the High Court in Glasgow have listed 14 charges in a seven-page indictment of accusations which span between January and September 2020.

The trial, which began on Monday, has heard how in September 2020, Border Force officials discovered a tonne of cocaine hidden in a banana box shipment.

The shipment had arrived at Dover from Ecuador and was addressed to a business in Glasgow.

In the boxes, they found 119 foil packages containing 952kg of cocaine with a purity level of 73%.

Three-day search found tonne of cocaine in banana boxes, court told

More stories from glasgow & west scotland.

The drugs were concealed in deliveries of fruit destined for the “Glasgow Fruit Market” at an address in the city’s Townhead.

Dirty money is said to have funded the set-up involving the purchase of equipment, leasing premises, buying cars and registering company directors under fake names for the “Glasgow Fruit Market”.

It is alleged James Stevenson, 59, headed up the operation and teamed up with another man for the “collection, storage and onward transmission” of £1.04m of criminal funds.

Jurors were told that in April 2020 the home of Laura and Brian Noble in Glasgow’s Robroyston was found to contain £1.15m in cash.

A total of £996,060 of the cash was kept in heat-sealed plastic packages, and DNA and thumb prints belonging to Laura Noble’s brother Stephen O’Donnell was found on some of the bags.

A search of O’Donnell’s home in the city’s Lambhill found a total of £76,320 of cash of which £70,070 was kept in heat-sealed packets.

The jurors were told that O’Donnell later pled guilty to possession of criminal property of £1,092,290 and received a two-year prison sentence.

James Stevenson has denied directing O’Donnell to be involved in money laundering.

He has incriminated John Gurie in his special defence for two charges involving serious organised crime and cocaine.

The jury was told that Gurie was jailed for six years in 2020 after police searched his home, car, van and a lock-up garage and found various quantities of cocaine, cash, and a hydraulic press used to bind together powdered adulterated drugs.

Further special defences of incrimination have been lodged by James Stevenson against Lloyd Cross, James White, and Stephen Jamieson whose present whereabouts are unknown.

The trial before Judge Lord Ericht continues.