Jeanneau Sun Odyssey 35 Yanmar 3YM30 engine oil leak.

[Willie D.]

Hi Folks.

I have an engine oil leak between the gearbox and the engine.  The gearbox and drive plate have been removed to reveal the flywheel which I also need to remove.   Does the flywheel position need to be marked carefully in relation to the engine before removal. Assuming the leak is coming from the rear crankshaft oil seal will the seal be easy to remove and renew.  Is there a possibility that the leak may be coming from somewhere else behind the flywheel.  

Any advice would be very gratefully received.

Best regards.

Willie D.

[Charlie-Bravo]

Hello Willie
Not had to do this yet on mine, so you might find better advice from others, and having removed the gearbox you obviously are fond of the spanners and enjoy the challenge! and am not attempting to teach you the sucking of eggs.

looking at the Yanmar workshop manual, the seal being located in the flywheel bell housing casework will involve removing the bell housing casework to install the seal, fitting the seal it's self will be easy enough, just a bit more spannering to get the case off, I could be wrong but engine seals are generally put in from the oily side of things, .... bike crankcase seals and gearbox seals always seem to be like that, guess they might remove themselves otherwise, the only exception might be if the gearbox holds the seal in place, but that's just wishful thinking.
 
If you don't have a manual you can find it via google, the one I have came from

 j109.org/docs/yanmar_3ym-2ym-service-manual.pdf

always nice to have a book with lots of pictures to help , and it has a nice section on how to take the whole thing apart and put it back together again.

I wouldn't think there are many other places for the oil to escape behind the flywheel other than the seal, it is the most likely cause, although not a 'common' fault of the engine, but seals don't last forever, perhaps others know better.
No mention in the instructions about marking the flywheel position, perhaps it can only go on in one place, but no harm in making your own marks.

Good luck with it, and let us know where the leak came from , seal or mystical other place.

CB

[Willie D.]

Hi Charlie-Bravo.


Thanks for the information.  I have downloaded the manual and printed the relative pages.  It looks fairly straight forward - fingers crossed.  I will let you know how it goes.


Regards.

MB 

[vasko]

On my Sun Liberty 34 with VP2003 I had to change this seal twice with about 800h between changes - this time I need also to change the two seals on the gearbox also - e.g in brief as your gearbox is out you may also change the gearbox seals also... I did mark the flywheel to reinsert at the same place to play it safe... also the main factor that affect the seal longevity is how often you change your engine oil as the old worked oil is actually affecting the seal slowly...

[Willie D.]

Hi.

Many thanks for the information.  That's a good point about the gearbox seals.  Perhaps I will change those too.

MB.