Engine Mounts vs Dripless seal

Engines, Drive trains, Propellers, Steering, Ground Tackle and other mechanical system
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capt446
Posts: 12
Joined: Thu Sep 03, 2020 11:22 pm

Engine Mounts vs Dripless seal

Post by capt446 »

Hello all,
Just purchased P35 "Deja Vu" and had a great sail from Ft Pierce to our homeport of Melbourne FL.
As part of the survey deficiencies the previous owners replaced the Yanmar 3GM engine mountings which are connected to a PSS dripless seal. The seal does not leak up to 1100 engine rpm but above that sprays water from the forward end. Additionally, I can put pressure on the transmission housing and cause the seal to leak even when the shaft is not turning.

My mechanic here thinks that the wrong engine mounts were installed and that the dripless seal is misaligned. He recommends removing the present mounts and installing less flexible engine mounts.

Anybody out there replaced their engine mounts and connected to a dripless seal?

Best regards,
Andy

Mark K.
Posts: 29
Joined: Sun Jul 31, 2016 4:32 pm

Re: Engine Mounts vs Dripless seal

Post by Mark K. »

When I replaced the original engine mounts on my Yanmar 3GM30 the dripless propeller shaft seal started leaking badly. What happened was the while replacing the mounts the engine shifted forward slightly so that the bellows were not longet compressed very much and therefore reduced the sealing pressure on the shaft seal. Loosening the fore/aft adjustment on the mounts and levering the engine aft back to where it should have been stopped most of the leak. Of course check and adjust the alignment as necessary. I did need to move the stainless steel collar on the shaft seal back as well to further compress the bellows to stop the leak altogether. The bellows do not last forever so check and see what the replacement interval on yours should be. If you are going to have align the engine anyway it may be time to replace the bellows.

capt446
Posts: 12
Joined: Thu Sep 03, 2020 11:22 pm

Re: Engine Mounts vs Dripless seal

Post by capt446 »

Thanks very much, Mark. Sounds like I am in the same position.
How difficult was it for you to replace the bellows?

Best regards,
Andy

Mark K.
Posts: 29
Joined: Sun Jul 31, 2016 4:32 pm

Re: Engine Mounts vs Dripless seal

Post by Mark K. »

I didn't try to replace the bellows when I replaced the engine mounts since I was able to stop the leak by moving the engine aft then the stainless steel collar back a bit as well (not to mention the boat was in the water). One problem I found was I wanted to replace all 4 stainless steel Allen head set screws - which I believe is recommended. Single use screws. Discard used ones. Only two lock to the prop shaft the other two are set on top of the first two to lock them in place. However the inner two set screws only loosened a couple of turns and were impossible to remove. I was able to get some lok-tite on the threads and after 2 years nothing has moved. Ideally if I were to do the job again I would have the dripless packing loosely installed first, then align the motor then after that go and compress the bellows to specification.
I did go with motor mounts that are stiffer than the originals. It did require setting the idle speed to 1000 RPM since anything below that made horrible rattling noises in the boat.

capt446
Posts: 12
Joined: Thu Sep 03, 2020 11:22 pm

Re: Engine Mounts vs Dripless seal

Post by capt446 »

Thanks very much, Mark.
Replacing the mounts this coming Wednesday and will publish the results in case others find the same problem.

Best regards,
Andy

Freedom 35 (P) Deja Vu

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