Dripless shaft seal owners beware.

[er9]

Originally Posted by GILow

Pressure is simply a product of the depth below the waterline that the seal is situated. The make of seal does not change that.

My type is a PSS and the compression pressure is about what you’d expect, kinda firm, not particularly high or low. But yeah, the water comes out in quite a spray when I burp it.

It certainly sounds odd to me. I’ve thought about it a bit more and I wondered if maybe something small like a bit of seaweed might have somehow become trapped between the faces to allow that sort of seepage. My high school chemistry tells me salt crystals would have been washed out faster than they could form. I have trouble imagining them building up and causing a leak.

Oh, and sorry if you know this already, but just in case, most of these seals require that you replace the grub screws if you loosen them or reset the seal on the shaft, so do make sure you have fresh grub screws on hand if you do find you have to move the seal to adjust the compression.

I also fit a shaft anode in front of the seal as a fail-safe if the seal disk locking grub screws fail.

thanks...great advice...much appreciated on both. going to get an anode this weekend. i do have enough room for one in front of that seal disc. boat will be coming out of the water in a couple of months anf thinking my (unknown how old) dripless is going to be replaced with a PSS type with vent hose. think im overdue.

im starting to agree something got lodged between the rings and probably wasn't salt. i suspected salt first because the bottom of the carbon ring has a nice chunk of salt built up on it. when i burped it after i noticed the leak it got considerably worse so might have been a chunk of weed or garbage or something in there but i couldn't get it to stop dripping till i ran the engine.

that accumulated salt on the bottom of the carbon might be a sure sign its not compressed enough though its not visibly leaking.

[er9]

Originally Posted by wingless

Doesn't the boat have automatic bilge pump(s) that would conceal this low ingress dripping?

If those pump(s) / switches are not operating properly, then those problems should be immediately corrected.

thanks pumps are working. i had been working on the raw water system for a while so bilge had been regularly wet and think it hid the beggining stages of the leak and allowed it to get worse.

pumps would have kept up with leak at the dock but i could imagine, as some people do, leaving the boat for 6 months or so over winter etc...if i ever plan to leave the boat un-attended for long period it would now be at top of my list of things to take care of, checking/maintaining that sealing surface.

[er9]

Originally Posted by Symphony

I have had 4 PYI PSS dripless systems in 4 different boats over the past 20 years. Older models need to be burped after haul-out, newer models have a small hose vent. Spec was a bellows life of 6-7 years, but none of mine ever needed replacement as they looked excellent even after 10 years. Clean the faces of the bearing in or out of the water, take a look at it when the engine is running - if there’s trouble or debris in the bearing you’ll see a fine mist blowing salt on your bilge and marine gear.

Consider the system and bellows like a large thru-hull, checking the bellows and its connections at both ends. Total failure of a bellows would be catastrophic though due to lack of any valve at the hull. They are very nice and allow for a dry bilge with no problem, but I know an expert delivery captain who despises them after a near sinking.

I’ll keep them on my current boat but I check them every time I get on board.

i have been thinking lately about how to do an emergency repair to a catastrophic bellows failure.

My solution was to buy three large mountain bike inner tubes, cut them on both sides of the air valve stem, removing the stem. then i sliced them once the length of the inner tube to create one long, flat piece of rubber i could quickly wrap around the bellows.

i figured i could then cinch a couple rolls of that emergency silicone tape around the rubber inner tube to seal it off. also have about five wax toilet rings i could use first to stop the bulk of a leak.

funny thing i had bought all of this a couple of weeks ago and had it sitting on the settee. i hadn't had a chance to slice the inner tubes yet. you should have seen me cutting them once i discovered the leak. i would have made any benihana master ginsu chef proud.

[Don C L]

Some years back there was a thread about a boat that sank in San Diego due to a dripless shaft seal leak... have to see if I can find it...

[bobnlesley]

Originally Posted by Scaramanga F25

I just do not trust this type of seal. I never have had a problem with the traditional stuffing box type in 41 years. You can even repack in the water.

Our first yacht had a non-drip BMW seal/bearing assembly - I've never seen another anywhere - which worked brilliantly, but this one came with a stuffing box that I would've swapped out had I not received some sage advice just in time:
Dripless seals are only dripless until something goes wrong and at that point they can fail/leak catastrophically. Stuffing boxes might drip a bit, but even a serious failure/leak is unlikely to be catastrophic and as Scaramanga points out, they're repairable, even if afloat and/or out in the boondocks.

[rbk]

The idea that anything on a boat is “set and forget” is shear stupidity imo, more so below the waterline. Even your hull needs regular inspection and care. If you look at most failures of just about anything, chances are they are either improper installation, user error or lack of maintenance.

[sailcrazy]

We've had the PSS Seal in place since 2002. No real issues, but the bellows get stiff and lose their springiness, so we've followed the PYI directions of replacing it every 6-7 years. But we have had the set screws slip, allowing the bellows to relax and allow a leak. I ended up installing a circular zinc on the shaft just in front of the carbon ring, and have had no problems since. Also, PYI directed me to use wet/dry 100-150 grit sandpaper to resurface the carbon seal every 2-3 years. Just pull the bellows back a little, insert the sandpaper, and turn the driveshaft by hand for 5-6 revolutions. It puts a new face on the carbon seal and makes for a better seal. Works good!

[er9]

Originally Posted by sailcrazy

We've had the PSS Seal in place since 2002. No real issues, but the bellows get stiff and lose their springiness, so we've followed the PYI directions of replacing it every 6-7 years. But we have had the set screws slip, allowing the bellows to relax and allow a leak. I ended up installing a circular zinc on the shaft just in front of the carbon ring, and have had no problems since. Also, PYI directed me to use wet/dry 100-150 grit sandpaper to resurface the carbon seal every 2-3 years. Just pull the bellows back a little, insert the sandpaper, and turn the driveshaft by hand for 5-6 revolutions. It puts a new face on the carbon seal and makes for a better seal. Works good!

interesting. going to try that with the sandpaper this weekend.

[stromatolite]

Although unlikely, failure of the corrugated rubber seal part of the PSS was a concern when I installed mine... unfortunately there was not enough room to consider the traditional stuffing box. For piece of mind (albeit possible overkill), I installed at the same time a length of wheel-barrow tire inner tube and fastened one end of it with hose clamps around the stern tube (ie just beyond the PSS connection to stern tube). It was cut long enough to extend towards the engine coupling. I then folded it back upon itself a couple of times until completely out of the way. Failure is presumably more likely under forces imposed from an operating engine and therefore I will be on the boat... so the plan would be to pull the inner tube piece forward over the leaking seal and fasten it with another hose clamp or two to the propeller shaft. In short, I have a rubber hose containment system pre-fastened at one end and ready for deployment to slow down water ingress while I think about the next step. Engine use may subsequently be out of the question but I might be able to hose clamp it to the non-rotating carbon part of the PSS seal housing to regain this. Regardless, the engine would also become useless after a foot or two of water.
As for the OP concern, on possibility is if the rubber seal was not compressed enough... I think for a 1" shaft the compression is supposed to be about 3/4". The two surfaces of carbon and steel rotor also have to 'wear' themselves together, so as noted if the shaft was not turned subsequent to repairs, a leak might be possible, that said, I suspect it would be a drip, not a pour.

[er9]

Originally Posted by stromatolite

Although unlikely, failure of the corrugated rubber seal part of the PSS was a concern when I installed .....ur.

that's a fantastic idea. I think when my new shaft seal goes in I'm going to do the same.

I remember reading on some forum about a guy who's shaft seal tore in half when he started the engine I believe it was.... I think if catastrophic failure like that happened, jamming it into gear to stop th he shaft from spinning and rolling/clamping the inner tube over it may be a very effective solution. if you could get it clamped to the carbon stator I dont see why that wouldn't work as a temporary seal assuming its strong enough to hold back the water pressure.

[sailcrazy]

But..on the other hand, could all that folded inner tube and stuff get caught on the spinning shaft and really tear something up??? We've had the PSS Seal on our boat for a long time (2002). The only issue we've had is the set screws coming loose, allowing the boot to relax and a dribble of water leak into the bilge. The bilge pump alerted us to the issue (it is located where I can/do monitor it when we're underway) and it was quickly resolved.....and now we have the circular zinc on the shaft just in front of the fitting, so it can't happen again. We do leave our boat for 5-6 months each year, but when we resplash I check the thru-hulls and open them, then burp the shaft seal by pulling it away from the carbon block to let the air out. Never had an issue and never heard of anyone having that issue. Are you creating a potential problem rather than fixing one? Your boat, your choice!

[David M]

Never have a problem with my PSS seals for many many years, but then the boat gets a lot of frequent use. In my experience, the seals need a few pounds of pressure between the carbon and stainless steel rings. A raw water injector from the boats raw water pump is necessary first to keep relatively unoxidized water out and to eliminate any bubbles that get in there. Stainless is less likely to corrode in an environment where there is oxygen....I know that sounds counter-intuitive.

[stromatolite]

Thanks er9, although I recall the idea initially came from looking at a Manecraft seal design which had some means of backup should the rubber fail, and I just tried to come up with something to do the same. I have a piece of blue 'lay-flat' rubber discharge hose and a short length of corrugated metal wrap that was part of some plumbing pipe coupling should I need to reinforce the inner tube against water pressure. As noted, overkill, and I doubt it will ever happen as inspection shows the rubber to be in great shape but... it could leak a lot if... and why not? As for getting wrapped around something, a fair thought... but by the time the inner tube is folded back upon itself a couple times it becomes quite a stiff rubber collar and located at the end of the stern tube well away from all the rotating bits and not a concern. A couple of zip ties might serve to secure it all in place otherwise.

[GILow]

Originally Posted by David M

... A raw water injector from the boats raw water pump is necessary first to keep relatively unoxidized water out and to eliminate any bubbles that get in there. Stainless is less likely to corrode in an environment where there is oxygen....I know that sounds counter-intuitive.

Sorry David M, but I do not agree with this. According to the manufacturer, the PSS only requires forced water injection if the boat travels fast enough under power for the venturi effect of the passing water to suck air into the seal from the front. I cannot remember the speed, but at least 9 knots comes to mind.

The idea around unoxidized water is... interesting. But I'd like to see some supporting documentation or evidence for the statement. It is the first I've heard of such a thing and it was not mentioned in any of the PSS documentation when I installed my new seal about four years ago.

[Sailmonkey]

On the subject of water injection to the PSS.

While not required on our SLOW sailboat, I’ve had the raw water plumbed to the PSS for 10ish years. We normally operate our boat in the muddy waters of the Texas coast, a solution that’s akin to lapping paste over time. The water injection has served to keep the sterntube/shaftlog/cutlass nearing clean and unworn this whole time.

So while I wouldn’t bother with injecting water into it for a boat with a p-bracket mounted cutlass, it does seem to make a difference to those of us with a cutlass in the deadwood.