Your favourite (or least favourite) shaft seal.

[ItDepends]

All of the “leak free” shaft seals, either the lip seal or the face seal type, all have the same flaw as far as I am concerned for a shaft log application on a cruising boat. They all have a failure mode that, while very rare, is instantaneous and catastrophic. They can not be easily repaired in the water, much less at sea. Water can then come in at a rate that will very likely overwhelm your bilge pump.

A standard packing gland can not fail this way. It can leak, and it can leak quite a bit if ignored, but it really can not fail totally and quickly flood the boat.

Somebody is going to point out that the packing gland DOES have a catastrophic failure mode: the hose connecting it to the shaft log. But they ALL have this weakness, so it’s not a distinguishing characteristic.

If you want a dry bilge AND a standard gland that is easily achieved with “Dripless Packing” from Western Pacific trading. That is a product that has worked well for me in many applications.

[jordanbigel]

Originally Posted by mvweebles

Personally, after 20 years, I converted from traditional to PSS dripless simply because I aspire to a 100% dry bilge. I then decided to swap the PSS for a Tides lipseal style when I had some shaft work done even though the PSS had performed well for me. Why? I had seen a PSS failure due to improper install (collar slipped - easily prevented by putting a hose clamp behind it in addition to properly installing the double set screws). And I had seen a Tides leak after many years that was easily repaired with a standby seal. Finally, lipseals are very common and reliable types of seals - lipseals on crankshaft is what keeps oil inside an engine.

We use something similar, by Norscott - uses standard Parker lip seals (1 in rear 2 in front) but instead of water injection it uses oil (ATF). Never leaks, in 22 years. Have had to replace the seals every 5 or 6 years, and it is a PITA, and there is the risk of "rolling" the edges of the lip seal during installation which prevents it from sealing properly.

https://norscotshaftseal.com

The main advantage of this particular seal is it's low profile design - I tried to fit a PSS but it was too large for the shaft tunnel on my boat which is surprisingly narrow for a 50' boat (and shockingly hard to access!). The Norscott was the only seal that fit.

If I had a larger/wider shaft alley, I would not have chosen the Norscott since it's just so unusual and non-standard. But, having now used it for ages, I would choose it again even if I had the room for a PSS.

[jordanbigel]

Originally Posted by ItDepends

All of the “leak free” shaft seals, either the lip seal or the face seal type, all have the same flaw as far as I am concerned for a shaft log application on a cruising boat. They all have a failure mode that, while very rare, is instantaneous and catastrophic. They can not be easily repaired in the water, much less at sea. Water can then come in at a rate that will very likely overwhelm your bilge pump.

On my shaft seal, both the outer (aft) lip seal and the 2 inner (fwd) lip seals would all have to fail before water enters the boat. Highly unlikely. In 22 years has never happened. I have have had the outer lip seal leak so that water enters the shaft seal and displaces the oil (I ran that way for 3 months before replacing the seals), but never had the 2 inner/fwd lip seals fail or any water enter the boat.

Yes, these cannot be repaired in the water. A flaw, I agree.

[MicHughV]

As above...I have personal experience with a standard shaft seal...the PSS shaft seal and the dripless variety and they all work great, sorta kinda.

Here's the thing, if you find yourself in an out of the way place, and a problem develops with the PSS or dripless variety, you'll be hard put to fix or repair it.

A standard stuffing box is a thing you can always repair yourself, by adding new flax, tightening up the packing gland nut, etc.
These days, you can get a teflon impregnated flax that is pretty much bullet proof. I've tried it and liked it.

The PSS shaft seal and dripless are wonderful...when they work...they work great.....but anything goes wrong, and they develop a leak, fixing them is a major issue.

Of the three, the standard stuffing box gets my vote.

[wingssail]

I have used standard shaft packing for 40+ years. It is often a pain in the tail. If there is water in the engine bilge it usually came from the packing but I keep using it out of familiarity and simplicity. I can replace the packing or adjust it in the water and at sea.

[Bill O]

We have a Lasdrop (with the water feed from the motor) and it works well. It came w/the boat and we just changed it out for a new one this year. The bellows do not need to be changed as often as many other brands and we hope to not need to touch it again for another 10 yrs. (especially when you add a synthetic cutlass/stern tube bearing).

That said, there is simplicity to a standard stuffing box and the ease of changing the packing in the water. Most of my other boats had a stuffing box and it was very easy to maintain. The only one that was a pain, was one with a v-drive since it was difficult to get wrenches in spot.

[skipperpete]

I think my rejection of the shaft seal in my earlier post needs some explanation. I’ve been a marine engineer for a long time and a large part of my business is replacing engines that have either died young or have reached a point where it was no longer financially viable to rebuild them and the replacement process requires that the newly installed engine is connected to a reliable series of systems.... fuel system ; raw water supply and vent loop; controls and cables; exhaust system; engine beds and usually the propeller, the shaft and the shaft seal. No owner is going to be happy when his new engine install fails because any one of the previously listed items craps out a month or 2 later and the boat has to be lifted and repaired. The stern gland is one of the high priority items and the one that I mentioned is a serial offender either from a wasted neck where it is connected to the prop shaft or where the bellows has been damaged/cut by the closest “neck” hose clamp due to efforts to apply more compression to the bellows to stop leaks. All of the other types of seal.... PSS, Volvo, lip seals, lasdrop, ceramic with spring and the conventional I have no problem with........ just this particular one and I’m happy to hear that some people have had no trouble with em.
Pete.

[Bill O]

Forgot to mention in my last post the newer "bellows" for the Lasdrop isn't an accordion type rubber that you typically see in the dripless shaft seals. It is now a heavy duty Trident exhaust/water hose (#202V) and is similar to a standard stuffing box hose.

[GILow]

Great responses so far, thank you all.

I’m currently running a PSS on the other boat. It has been trouble free but it does worry me slightly.

So far I’d say the majority are in favour of the traditional setups, and I can see the merits.

The Volvo seal has caught my eye, it looks less likely to give trouble than the PSS while still having the potential for a dry bilge.

[Bowdrie]

As few boats today have an actual "tube" that the shaft runs in between the packing gland and the stern bearing, this has fallen into disuse.
With old boats that had such a tube/shaft alley, it was common to fill the tube with either thick grease or pour it full of melted tallow, (like canning wax,) until it squirted out the Cutless bearing.
Done either way the inside packing could run quite loose and still not leak and would last almost forever.
The grease is easier to deal with in most cases.
With grease a Zerk fitting allows giving a pump or two once in a while.
Both ways also keep the "nasties" out of the alley.
Another seagoing feature lost in time, sigh.

[skipperpete]

Originally Posted by Bill O

Forgot to mention in my last post the newer "bellows" for the Lasdrop isn't an accordion type rubber that you typically see in the dripless shaft seals. It is now a heavy duty Trident exhaust/water hose (#202V) and is similar to a standard stuffing box hose.

Thanks for that info on the Lasdrop gen 2, they eliminated the the setscrews and bellows completely... nice upgrade but only for shafts 30mm and up.

[MicHughV]

I have the Volvo seal on my Beneteau, as the original engine was a Volvo...since then replaced by a Yanmar.
It doesn't leak per se, but one can see moisture emanating from the front of the seal when the engine is running. I have an oil absortion mat under the engine, and I can feel that it is wet near the transmission shaft coupler after the engine has been running for a period of time.

I have a spare seal, so I have been able to peer inside to see what makes it tick.
First thing that came to my mind, is that the propshaft needs to be perfectly aligned for this seal to function properly and efficiently.
It should be aligned perfectly anyway, but a packing gland type seal can stand a tiny bit of misalignment better than this type of shaft seal imo

After you've hauled your boat, the Volvo seal needs to be "burped" as there will be an air pocket in there, as the seal requires water for lubrication much like a cutlass bearing. Some of these seals come with a flexible mini tube that attaches to small thru-hull for this purpose.

All this being said, I've installed a bilge "alarm" which goes off when the bilge pump float switch activates, such is my paranoia about this seal. I bought the boat with this seal already in place, but plan to swap it out at the next haulout.

But...that is my viewpoint. Others' may differ.

[Bill O]

Originally Posted by MicHughV

After you've hauled your boat, the Volvo seal needs to be "burped" as there will be an air pocket in there, as the seal requires water for lubrication much like a cutlass bearing. Some of these seals come with a flexible mini tube that attaches to small thru-hull for this purpose.

I believe all the dripless seals need to be burped after a haul out to get the air out otherwise they will overheat w/o water/air trapped by the seal. Luckily it is very easy to do. We have the "high speed fitting" that allows engine water to be injected into the seal and it is still a good idea to burp it before leaving the lift area.

[MicHughV]

Though I've not done this, I read about this idea, where you take a plastic straw, fill it with waterproof grease.....not sure how you would do this, but let's assume you can, maybe with a plastic syringe or something, then squeeze the ends of the straw flat so that you can insert it under the lip of the Volvo seal, between shaft and seal and milk the remaining grease out to inside the seal.
Obviously, you'll have some water come into the boat during this procedure, but with luck, you can place a good dollop of grease in there.
Why do this ?.....to fix a possible leaking seal....

Sure would like to hear if anyone has done this or thinks it's worthy of an idea.

[ItDepends]

Originally Posted by MicHughV

Though I've not done this, I read about this idea, where you take a plastic straw, fill it with waterproof grease.....not sure how you would do this, but let's assume you can, maybe with a plastic syringe or something, then squeeze the ends of the straw flat so that you can insert it under the lip of the Volvo seal, between shaft and seal and milk the remaining grease out to inside the seal.
Obviously, you'll have some water come into the boat during this procedure, but with luck, you can place a good dollop of grease in there.
Why do this ?.....to fix a possible leaking seal....

Sure would like to hear if anyone has done this or thinks it's worthy of an idea.

If you think this will "fix" a leaking lipseal I have a bridge in Brooklyn for sale cheap I am sure you'd be interested in as an investment.