Prop Shaft Leak

[jamrocksailing]

Hi all, we avoided a near disaster today, went out for a quick sail, and then while packing the yacht up in the mooring I always check the bilges. To my shock, they were full up of water.

I discovered the engine prop mounting was leaking and had been probably since we set out from the mooring. The bilges were dry when we set off!

Can anyone offer advice, attached is a pdf with a couple of pictures. There is a shot taken prior and one after the leak, you will notice that a solid metal bracket has turned and you can now see a screen hole in it. The join is where the leak is coming from.

I managed to stop the leak by changing the position slighting by wedging a screwdriver under it but need to of course urgently resolve it but unsure of the problem.

If anyone can offer any solid advice would be great, the yacht is in Kingston Yacht club so no dry dock available other than on the trolley so you cant leave it out the water.

Thanks kindly all and happy new year.

[Dsanduril]

That's a PSS Dripless shaft seal. https://www.shaftseal.com/pss-type-a-seal.html

The rotor on the front is the shiny steel bit, it spins with the shaft, the part just behind it is a carbon stator. The two are supposed to be very, very flat, and that is what provides the seal. Please grab the direction from the PSS site, but short answer, two things you can try:

1. slide the carbon part back, making the gap where it is leaking bigger. The rubber bellows should allow enough give where you can get a gap of 1/8" (3mm) or so. This will let a lot of water into the boat. It will also allow the water to flush out any debris that may be between the two sealing surfaces. Close it back and see if it seals.

2. Compress the bellows a little more. If they are old they may not be applying enough force on the seal. There are two sets of set screws on the rotor. If installed properly there are two set screws in each hole. Remove the "top" ones entirely then slightly loosen the bottom ones. Slide the rotor aft 1/8-1/4" (3-6mm) this compresses the bellows a bit more. See the manual for all the details.

And probably plan on replacing the seal at the next haul out (which may be very soon if neither of those things work to hold you over for a short time).

[Edit] and it looks like in the second photo something has really been chewing up the carbon, it really shouldn't show any wear at all. The little tube is supposed to vent air (slow boats) or provide forced/pumped water flow (fast boats), to make sure there is water at the sealing surface, make sure the tube is not clogged. And from what the carbon looks like in the photo, you may be in for a haulout.

[jamrocksailing]

[Thank you kindly for the detailed reply. Agreed looks like something not be right. Was going to haul out to clean the bottom so timing is right
Just need to ensure I can seal it till that happens.

The screwdriver lifts the shaft a bit and this stops the water. The solid ring in front of the carbon piece also turns freely.

Will have a look at the link. Happy new year.

Originally Posted by Dsanduril

That's a PSS Dripless shaft seal. https://www.shaftseal.com/pss-type-a-seal.html

The rotor on the front is the shiny steel bit, it spins with the shaft, the part just behind it is a carbon stator. The two are supposed to be very, very flat, and that is what provides the seal. Please grab the direction from the PSS site, but short answer, two things you can try:

1. slide the carbon part back, making the gap where it is leaking bigger. The rubber bellows should allow enough give where you can get a gap of 1/8" (3mm) or so. This will let a lot of water into the boat. It will also allow the water to flush out any debris that may be between the two sealing surfaces. Close it back and see if it seals.

2. Compress the bellows a little more. If they are old they may not be applying enough force on the seal. There are two sets of set screws on the rotor. If installed properly there are two set screws in each hole. Remove the "top" ones entirely then slightly loosen the bottom ones. Slide the rotor aft 1/8-1/4" (3-6mm) this compresses the bellows a bit more. See the manual for all the details.

And probably plan on replacing the seal at the next haul out (which may be very soon if neither of those things work to hold you over for a short time).

[Edit] and it looks like in the second photo something has really been chewing up the carbon, it really shouldn't show any wear at all. The little tube is supposed to vent air (slow boats) or provide forced/pumped water flow (fast boats), to make sure there is water at the sealing surface, make sure the tube is not clogged. And from what the carbon looks like in the photo, you may be in for a haulout.

[Sailmonkey]

The solid ring should not turn freely, it should be affixed to the shaft. Inside of the holes on the solid ring are (or should be) set screws that hold the ring stationary on the shaft, the ring should turn with the shaft.

https://m.youtube.com/watch?v=yGDk5lXGBFE

Here’s a video of the pss seal installation.

[bensolomon]

The set screws are not made to bite twice. If it is loose, it must be replaced. It is possible that your prop shaft is also out of alignment, or your prop has picked up some barnacles or debris or and is causing excess vibration this leading to the PSS shaft seal leaking.

It's likely that without the engine running and the shaft turning, the leak won't happen, but what you have there is a real problem and should be fixed ASAP.

Get a C clamp, compress the bellows and then use the c clamp on the shaft to hold everything in place while you tighten the set screws. I can't emphasize enough.....those screws are not made to be set more than once. Also, there are o rings that will have to be replaced. And....the bellows have a life span of 6 years, I think. So.....replace everything.

I am not a boat mech......just own a 30 year old boat and have faced the same issue you are.

Ben

[jamrocksailing]

Originally Posted by bensolomon

The set screws are not made to bite twice. If it is loose, it must be replaced. It is possible that your prop shaft is also out of alignment, or your prop has picked up some barnacles or debris or and is causing excess vibration this leading to the PSS shaft seal leaking.

It's likely that without the engine running and the shaft turning, the leak won't happen, but what you have there is a real problem and should be fixed ASAP.

Get a C clamp, compress the bellows and then use the c clamp on the shaft to hold everything in place while you tighten the set screws. I can't emphasize enough.....those screws are not made to be set more than once. Also, there are o rings that will have to be replaced. And....the bellows have a life span of 6 years, I think. So.....replace everything.

I am not a boat mech......just own a 30 year old boat and have faced the same issue you are.

Ben

Apologies for the delay, I have managed to look at it all extensively now. The good news is that I have a brand new one so when I pull the yacht out I will replace.

It is holding now, I have just not engaged the engine, will only do this when I take round to the clip for the hauling out at the end of this month.

The learning curve is still steep but when things like this happen you get that additional knowledge for next time.

Thansk kindly for the reply.

[jamrocksailing]

Originally Posted by Sailmonkey

The solid ring should not turn freely, it should be affixed to the shaft. Inside of the holes on the solid ring are (or should be) set screws that hold the ring stationary on the shaft, the ring should turn with the shaft.

Here’s a video of the pss seal installation.

Hi, thanks yes I had a look online and now fully understand the system. I have a brand new one that I will fir when I haul the yacht out the end of this month. I was thinking about loosening the screws on the stainless rin and sliding aft a tiny bit but don't want an issue if that does not sit right or the screws don't tighten. Will just replace it all when I take it out.

[stormalong]

How much time between photos 1 and 2?

Looks like it has been leaking for a while. It would be worthwhile to compress the bellows a bit more right now. Yes, PYI recommends never re-using the set screws. Probably for liability reasons. I have adjusted the ring position on mine without replacing the set screws and it has been fine.

As already said there are two set screws in each hole. The second one is to act as a lock on the first one.

It also appears that someone used a hose clamp as a safety. Be sure to reposition that after moving the ring.

[jamrocksailing]

Originally Posted by stormalong

How much time between photos 1 and 2?

Looks like it has been leaking for a while. It would be worthwhile to compress the bellows a bit more right now. Yes, PYI recommends never re-using the set screws. Probably for liability reasons. I have adjusted the ring position on mine without replacing the set screws and it has been fine.

As already said there are two set screws in each hole. The second one is to act as a lock on the first one.

It also appears that someone used a hose clamp as a safety. Be sure to reposition that after moving the ring.

Hi,
I was thinking I will compress a small bit and great to know you have been able to with yours. I need to check to ensure there are 2 screws as did not know that and they look very deep-set so might just be the one.

Was wondering if perhaps it has slipped back a tiny amount. Also, there is soundproofing on the inside of the floor board I think this was rubbing to create the wear. I will need to cut the section out of this to ensure nothing is hitting.

We live and learn. Thank you kindly for coming back.

[MicHughV]

be sure the bellows are compressed somewhat.....the only thing that holds the s/s disc against the carbon disc is water pressure....maybe move the s/s disc back a little, say 1/4" or so.......
the s/s disc...has...I believe ... two set screws....if one is missing it might allow the s/s disc to be micro out of whack....on top of the two set screws should be two other set screws...these keep the first set of setscrews in place...

sometimes, rare, but a tiny bit of dirt can find itself between the two discs...causing a leak.....you can push the bellows back to give it a quick clean....yes, there will be some water coming into the boat, but if you are quick, this will amount to little...

sometimes, I've seen a small air pocket form inside the bellow....usually, after a boat is hauled.....you have to " burp" the bellow to ensure there is water inside...

[stormalong]

Originally Posted by MicHughV

be sure the bellows are compressed somewhat.....the only thing that holds the s/s disc against the carbon disc is water pressure....maybe move the s/s disc back a little, say 1/4" or so.......
the s/s disc...has...I believe ... two set screws....if one is missing it might allow the s/s disc to be micro out of whack....on top of the two set screws should be two other set screws...these keep the first set of setscrews in place...

sometimes, rare, but a tiny bit of dirt can find itself between the two discs...causing a leak.....you can push the bellows back to give it a quick clean....yes, there will be some water coming into the boat, but if you are quick, this will amount to little...

sometimes, I've seen a small air pocket form inside the bellow....usually, after a boat is hauled.....you have to " burp" the bellow to ensure there is water inside...

The compressed bellows holds the SS ring against the carbon ring.

The OP has the high speed version of the PSS so the air bleed is not a problem.

[osprey877]

The OP has the high speed version of the PSS so the air bleed is not a problem.[/QUOTE]

Just make sure the open end of the air vent tube is above the waterline

[GreenWave]

Originally Posted by MicHughV

be sure the bellows are compressed somewhat....

sometimes, I've seen a small air pocket form inside the bellow....usually, after a boat is hauled.....you have to " burp" the bellow to ensure there is water inside...

I have heard about this bellows burp thing but honestly don’t know how to do it exactly. Is there a procedure?

[MicHughV]

the fact that the screw driver placed under the bellows stops the leak, would appear to indicate that the two surfaces are not mating properly, a situation compounded while running....what is causing this is hard to say without being there...

I would try to run the engine in gear while docked with the screw driver in place...maybe the bellows are worn ??

I noted the high speed version, but not sure why a sailboat has the high speed version, usually that little hose provides added water pressure from the outside due to high speed, as water can get sucked out of the bellows at high speed...that little hose is usually fitted with a little scoop over that little pipe outside of the hull to help feed water to the bellows.....I don't think that little hose is to bleed water and certainly not air to the outside of the hull....but in this case, it could also be venting water pressure to the outside of the hull...?? Maybe some little something got into that little hose and found its way to the bearing surface.

These are some of the things, I'd be checking....as well as possible dirt, debris, etc...

my first inclination would be to pull the bellows back to see if there was any small piece of shell, seaweed, something...interfering with a good seal....but the fact that the screwdriver stops the leak might indicate a problem with the bellows...

Unfortunately the boat must be hauled to check or replace this....could be done with the boat in the slings.....but I'd try to do some diagnosing sleuthing while the boat is in the slip...

[MicHughV]

to burp the bellow, just pull the bellows back from the s/s ring...this will allow water pressure from the outside to enter the bellow....making a little burp sound...

Usually, after a boat is hauled, the bellow needs to be burped as air can get trapped in there...

some boats....have a prop shaft that is not very deep below the water resulting in marginal water pressure inside the bellow........water pressure obviously increases with submerged depth...