PSS Dripless Seal: lubricate from suction or discharge?

demonboy

demonboy

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According to the PSS Dripless Seal installation instructions boats that do under 12 knots and do not have a bearing in the shaft log can get away with just a venting hose. However I have a bearing in the log so I am assuming I have to lubricate and cool the bellows using the raw water. Can I get away with piping it off from the suction side of the raw water (i.e. before it reaches the pump) or would that compromise the suction, necessitating an installation from the discharge side instead?
 
Hi mate.
I fitted a PSS on my last boat a decade ago: it ran perfectly for eight years until I sold her. There was of course a 'bearing' in the log...the cutless bearing. The seal was the self-burping kind which you have. There is no need for any pressurised feed. All the hose does is let the air out.
I've just double-checked the installation instructions: seems a bit ambiguous re consequence of log bearing on sail boats. My understanding is that if there's enough water coming through the log for a seal/gland to be necessary (and I presume you had one before and were very glad to have it), there's enough to lubricate it.
Belated happy new year.
 
If you do need to pump water in (no knowledge on that question) then it's surely obvious that you need to connect to the discharge side of the pump. If you connect to the suction side, it will be trying to suck water out!

Pete
 
All that is required is that water rises in the stern tube to ensure that the PSS is submerged. My little motor sailer has a bearing at the aft end of the stern tube inside the log, but I know that if I remove the packed gland the water pours past the bearing into the boat. Thus it is certain that the PSS will be OK without a forced supply. Ensure that your new Torlon bearing has longitudinal grooves and I think that all will be well.

One word of warning. If your stern tube has previously been greased it, the shaft and everything else must be totally free of grease before fitting the PSS. Hydrocarbons on the seal will prevent its correct action and burn the faces.
 
macd said:
Hi mate.
I fitted a PSS on my last boat a decade ago: it ran perfectly for eight years until I sold her. There was of course a 'bearing' in the log...the cutless bearing. The seal was the self-burping kind which you have. There is no need for any pressurised feed. All the hose does is let the air out.
I've just double-checked the installation instructions: seems a bit ambiguous re consequence of log bearing on sail boats. My understanding is that if there's enough water coming through the log for a seal/gland to be necessary (and I presume you had one before and were very glad to have it), there's enough to lubricate it.
Belated happy new year.
Click to expand...

My PSS seal has (had) no external pipe and has done about 8K hours in 29 years.
 
vyv_cox said:
All that is required is that water rises in the stern tube to ensure that the PSS is submerged. My little motor sailer has a bearing at the aft end of the stern tube inside the log, but I know that if I remove the packed gland the water pours past the bearing into the boat. Thus it is certain that the PSS will be OK without a forced supply. Ensure that your new Torlon bearing has longitudinal grooves and I think that all will be well.
Click to expand...

Thanks for the answers and a belated happy new year to you all too.

Vyv, the Torlon bearing is in the P bracket, not the log, but the log bearing has longitudinal grooves too. It's a tight fit but I've no doubt water would pour in through it. With the old stuffing box I could almost get a continual drip if I loosened it off enough. I'm assuming that's enough water to cool and lube.
 
macd said:
Sounds like time for a new bellows, then.
Click to expand...

When I fitted a new one, in 2012, it was totally unnecessary. The old one was visually perfect.
Mine was one of the earliest supplied in the UK, when they weren't bothering with pipes for slower revving shafts.
It does, occasionally, need burping, like a Volvo seal but far more intermittently.
 
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I fitted a PSS seal 6 years ago on my 48' yacht. It has the vent fitted. Never been a problem other than make sure the SS ring compresses the bellows. Mine slipped forward over the first season and suddenly I had a leak! My fault! They use a double grub screw locking system and must be well tightened. Never caused any other problems. Brilliant bet of technology. Much better than grease and packing!
 
The water feed is only necessary above a certain speed, which i think is 12 knots, due to the water effectively drawing away from the seal and cutlass bearing at higher speeds. If you take it from the suction side of your raw water pump then the flow would reverse, and this would not work at all at high speed when the flow is actually needed.

If you have a sailing boat then no feed needed, If its a power boat then yes. Excellent seals, just in the process of replacing the stbd on my boat now.

Be aware PSS recommend the rubber bellows be replaced after 7 years. Not saying they are not good for 30+, but would an insurer cough for a sinking if he found out the seal was past its use by date.

I reckon mine are at least 15 years old, and the only reason I have changed them is due to worn and failing cutlass bearings. With the shafts out it would be a folly not to replace the seal, especially on my boat as getting a shaft out and back in is the worse job I have ever had to do on this boat.
 
I fitted a PSS Seal 8 years ago and was thinking it was maybe time to renew the bellows.
Nothing wrong with the old one as far as I can see.
Cant seem to find a supplier of the service kit or anything less than a complete new system.

Anyone bought one recently?
 
My boat came with a bellows type seal and is fitted with water lubrication. A small bore pipe is taken off the discharge side of the sea water pump before going into the heat exchanger. Had to fit a shut off valve as a steady trickle of water flowed back when the pump body is open. This probably supports earlier statements that feed is not required at low speeds.
 
My new one is coming from Aquafax via Force Four as a complete seal.

If you go to the PSS maker website they have tables of the parts kit and complete seal by sizes. I would then ask Aquafax direct if they can get the parts kit.

My only concern for re-using the rotor and stator is possibility of damaging these upon removal, which due the seal's location within a bulkhead hole between the rear of the engine bay and after cabin sole void, is a real possibility. Changing the seals on my boat is almost enough to make me consider having Devil's Egg Whisks (outdrives).

Still got it all out now, and the re-assembly is a lot simpler and cleaner.
 
Hostage said:
I fitted a PSS Seal 8 years ago and was thinking it was maybe time to renew the bellows.
Nothing wrong with the old one as far as I can see.
Cant seem to find a supplier of the service kit or anything less than a complete new system.

Anyone bought one recently?
Click to expand...
I purchased a new bellows a couple of years ago. Ordered through Sillette Sonic, but AFAIK, sourced by them from Aquafax, as said above.
Cost about £70 for a 1" bellows IIRC. Quick delivery.
A word of warning, based on my experience. I found the new bellows to be very much stiffer than the old one, which was at least 10 years old. No way could I get the compression specified in the instructions, even with making up gadgets to help. I had to leave it several mm less, but seems OK.
Both Sillette and Aquafax agreed that the spec. seemed to have changed, but couldn't offer any other suggestion.
 
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Hostage said:
I fitted a PSS Seal 8 years ago and was thinking it was maybe time to renew the bellows.
Nothing wrong with the old one as far as I can see.
Cant seem to find a supplier of the service kit or anything less than a complete new system.

Anyone bought one recently?
Click to expand...

I e-mailed PSS in the States and got the full kit for about $80 - they even sent it as a "sample" so no customs or VAT. It took about 17 days to arrive in Greece from the US.
 
superheat6k said:
My new one is coming from Aquafax via Force Four as a complete seal.

If you go to the PSS maker website they have tables of the parts kit and complete seal by sizes. I would then ask Aquafax direct if they can get the parts kit.

My only concern for re-using the rotor and stator is possibility of damaging these upon removal, which due the seal's location within a bulkhead hole between the rear of the engine bay and after cabin sole void, is a real possibility. Changing the seals on my boat is almost enough to make me consider having Devil's Egg Whisks (outdrives).

Still got it all out now, and the re-assembly is a lot simpler and cleaner.
Click to expand...

No reason for concern - my rotor has been banged and dented and a quick re-facing in a lathe brings it up like new (and only cost €5 and took 30'). The carbon block is the original - no apparent wear after about 8K hours.
 
"Be aware PSS recommend the rubber bellows be replaced after 7 years. Not saying they are not good for 30+, but would an insurer cough for a sinking if he found out the seal was past its use by date."
People are always making remarks like this but my opinion is that, if you've inspected it and satisfied yourself that it's serviceable, the insurer could not demur. How would they know its age anyway?
 
When I changed from a Deep Sea Seal to PSS I decided to keep the water feed to the seal from the engine cooling water as my boat is on a drying mooring and sits in mud - flushing out the stern tube seemed healthier than having the steady ingress of mud into the cutlass bearing.
 
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