Dripless shaft seal leaking

[John BO]

My boat has been haulout for 6 months. Back to water, the dipless shaft seal is leaking.
1- What the purpose of the upper pipe (sea water from the engine ?)

2- Could the haulout have damage the seal ?
Thanks.

[fourlyons]

#1. On a low speed boat that hose is often a vent to vent air after launching. You want to vent the air so that water, which is what actually "seals" the shaft and lubricates the seal, can flow up to the seal. On high speed boats it's usually water injection, at high speed you run the risk of water getting sucked out of the seal.

#2 Not exactly, but having the boat sitting too long with saltwater on the seal surfaces can cause pitting in the stainless steel seal ring/face. The manufacturer of that dripless seal told me that is designed for commercial applications where the boats are in nearly continuous use and so the saltwater is always being renewed/re-oxygenated. That seal has a carbon face and a stainless steel face, they ride against each other and, when wet form a seal, but that combination risks crevice corrosion if the saltwater sits to long.
If you remove the stainless steel face it can be refaced/lapped.

[boatpoker]

Looks like a Lasdrop unit that has sat a while. If corrosion is light, squirting a couple of ounces of an abrasive cleanser such as Soft Scrub down that hose may polish up the seal enough to stop the dripping.

That hose is required to be connected to a water injection source in high speed applications only, otherwise (99%) of sailboats it is simply vented overboard well above the waterline. Even if it's not a Lasdrop unit I suggest you download the mfg. installation manual ... it will have some tips.

[mike d.]

I had the same problem ! before the boat was launched, I took a water bottle, and pulled back the bellows and wet the contact surfaces ! Did not have anymore problems after that ! It seems to me that when the boat is on the hard, the surfaces dry out, and if you don't get them wet before launch, then the surfaces don't seal, and also grind away the mating surfaces ! I may be all wet on this, but it worked for me !

[boatpoker]

Originally Posted by mike d.

I had the same problem ! before the boat was launched, I took a water bottle, and pulled back the bellows and wet the contact surfaces ! Did not have anymore problems after that ! It seems to me that when the boat is on the hard, the surfaces dry out, and if you don't get them wet before launch, then the surfaces don't seal, and also grind away the mating surfaces ! I may be all wet on this, but it worked for me !

Take another look, there are no bellows on that unit, thats why I think it's a Lasdrop and gave their prescribed action.

[MicHughV]

Another way is to get a plastic straw, fill it with grease, flatten the straw and insert under that seal and milk the grease out. Water pressure will keep the grease against the seal.

[MicHughV]

The old style dripless seals had the bellows, pushing two mating surfaces together but the newer versions don't have the bellows, they use a rubber seal.

[boatpoker]

Originally Posted by MicHughV

The old style dripless seals had the bellows, pushing two mating surfaces together but the newer versions don't have the bellows, they use a rubber seal.

As I said, that loooks like a Lasdrop unit, probably GenII, in which case no rubber seals and no bellows.

As with so many questions on here, the OP has failed to provide enough information that all gets are guesses rather than answers.

[mike d.]

when did it change ! Granted ours is 18 yrs old, but still does it's job !

[MicHughV]

My Beneteau has a dripless shaft seal, but it's not an old style bellows unit, made by PSS.
It doesn't look like the one in the photo either, but similar.
Though I've never tried to do it, I was advised to use the grease in straw method as outlined above to address a leak.
Other than that, if a leak remains, it is probably time for a new one, but hard to say from a single pic as there may be other issues, alignment, wear on shaft, etc, etc..