PSS Shaft seal vent pipe dripping

[AndyL]

Any ideas why the vent pipe might be dripping (when motoring)? It's well above the waterline right under the cockpit seating. Boat is a Marcon Cutlass 27 with a Yanmar 2YM15. Should I simply stick a cork in it?

 

[earlybird]

Strange effect, for which I can't offer an explanation, but on a Cutlass the vent isn't necessary, so I'd be tempted to put a cork in it.
Don't forget to re-vent if the boat dries out though.

 

[vyv_cox]

On some boats Volvo seals constantly require burping even though the boat has not dried out. It would seem that air is being driven up the stern tube by movement through the water. Maybe your PSS is suffering the same. I would definitely not block the vent as a second without water will kill the carbon side immediately.

 

[superheat6k]

The vent is in fact a lubrication water supply required for boats travelling above ~ 12 knots. So in your case simply seal it with a simple ball valve allowing you to burp the seal upon immersion after drying out or haul out.

Of course if you do find yourself sailing down hill with a very favourable wind behind you then remember to hook up the cooling supply (ex Sabre owner !).

 

[VicS]

Any ideas why the vent pipe might be dripping (when motoring)? It's well above the waterline right under the cockpit seating. Boat is a Marcon Cutlass 27 with a Yanmar 2YM15. Should I simply stick a cork in it?

This is what the website says:

Hose Barb​

For high speed vessels (12+ knots), a positive water supply is required to be plumbed to the PSS Shaft Seal for the purpose of lubricating and cooling the seal faces. Please review the PSS Shaft Seal Installation Instructions for more information on pickup points for water supply. In most cases, a slow speed boat (less than 12 knots) that does not have a bearing the shaft log does not require positive water feed and can simply be vented. Ideally, the vent line will be run at least 2-3 feet above the water line and will be as close to the center line as possible. This will ensure the vent hose is never below the water line, even with significant heeling. PSS Shaft Seal Installation Instructions has more more details on venting the seal.​

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[Roberto]

I found mine needs very little reverse speed to have drops of water coming out of the hose, whose end is at about 30cm above waterline

 

[pcatterall]

Any ideas why the vent pipe might be dripping (when motoring)? It's well above the waterline right under the cockpit seating. Boat is a Marcon Cutlass 27 with a Yanmar 2YM15. Should I simply stick a cork in it?

So, is that 2 or 3 feet as per the recommendation? It should be vented so I would not use a bung

 

[earlybird]

An open vent for a PSS seal on a typical sailing vessel is not essential.. Mine ran for 20+ years and 100s of hours of motoring with no vent or piped water supply.
During that time a bellows and an SS shaft rotor were replaced, but the original carbon seal remained in use.
The only attention it had was burping by pulling back the bellows when launching at the start of the season.
If a shaft bearing prevents water access to the seal, then a piped water feed might be necessary. That is a main purpose of the tube attachment.

 

[roaringgirl]

Extend the tube higher

 

[AndyL]

Extend the tube higher - I can't if it is to stay on the centreline. I am going to put a ball valve on it as superheat6k suggested. Thanks everyone.

 

[pcatterall]

An open vent for a PSS seal on a typical sailing vessel is not essential.. Mine ran for 20+ years and 100s of hours of motoring with no vent or piped water supply.
During that time a bellows and an SS shaft rotor were replaced, but the original carbon seal remained in use.
The only attention it had was burping by pulling back the bellows when launching at the start of the season.
If a shaft bearing prevents water access to the seal, then a piped water feed might be necessary. That is a main purpose of the tube attachment.

Not sure if this is the best advice. My PSS has been great over the last 3 years. The manufacturers advice about speeds in excess of 12 knots requiring a water supply is presumably because at that speed there may be insufficient water at the seal back even if there is no restrictive bearing. Yes I can imagine that, in your set up, 'burping' works. I wouldn't recommend that it is ok for everyone's set up though.

 

[Stemar]

Not sure if a ball valve will allow water up the shaft tube to lubricate the bearing. I'd be more inclined to extend the tube higher, even if it is off centre. Get it as high as you can and, I reckon that if you're heeling so much that the end is below the waterline, a couple of litres of water coming out of the tube will be the least of your worries!

 

[Boatface]

My PSS shaft seal vent pipe used to gush water but only when the drive was in reverse (prop driving water up the stern tube). So, hearing that venting might not be necessary in an 8 knot max boat, I blocked off the tube.
After our winter lift out, I didn't think to open it up again.
After about an hour or two's motoring the seal got so hot it seized for a moment and twisted the whole seal through about 90 degrees (we heard a loud "BANG" on deck). I had heard in the past that you could tell if a PSS was running dry because would make a loud screeching noise, but ours wasn't unduly noisy till it seized, after that it did squeal.
It got so hot that the prop shaft itself was hot to touch. Fortunately it didn't fail completely, so we didn't sink.
I've now put a Screwfix Bottle Air Vent (about £7) on the vent pipe so that it lets air though but doesn't leak when we reverse. This works fine.
To extend the vent pipe sufficiently to prevent leakage in reverse would have meant bringing it up another 2 foot or more, for which there isn't enough room or height available.