rear main seal???

[angie1015]

i am pretty sure i have a leaky rear main seal but i would like some feedback here.. 1982 larson omc 25'. bought a new motor this winter and rebuilt it. new crank, bearings, rings ect... it runs like a top. .however it leaks oil. if i am looking at the motor its on the left side... oil is shooting out pretty good. every 2 hours of cruising i leak out about a half quart... ( it looks like a hell of a lot more). the higher the rpm's the more it leaks. if i put my hand under the motor by the starter area i can see the drops of oil hitting my hand. i tried some stop leak but it did nothing. i have been using the boat for a few months and it has not got worse all season.. is there anything else it could be. before i pull the motor i wonder if there is anything else i can check. the flywheel turning is causing the oil to shoot out pretty good in the engine compartment...

 

[snake91876]

Re: rear main seal???

sometimes if you dont put a little silicone on the main cap ends where the rear main seal is it will leak. there is also the possibility that the rear main seal is turned facing out away from the motor when the lip should face in this would cause a leak like that, i would try tightening the oil pan bolts first.

 

[Scottaye]

Re: rear main seal???

You may want to check oil sending unit for leaks. Other than that, It sounds to me that you're going to end up pulling the engine. While it's out you should check all oil galley plugs in back of block for sealing. If they are ok, main seal time.

 

[superpop]

Re: rear main seal???

I replaced my raer main seal on my 4.3L which I think is the same as yours. IMHO the seal is a very poor design. The seal is comprised of a metal rib that is incased in rubber. If the metal rubs through the rubber to the outer mating surface you are going to get a leak. When I replaced mine I felt for the metal tabs that pierced the seal on the new gasket and installed the gasket with those tabs at 4 and 8 oclock as you look at the motor. The original seal had a tab that was installed at 6 oclock on the bottom and you could see the oil leak out when I pulled the bellhousing off. Pain to change but I am oil free in the bilge now.