Merc 260 HP Oil Leak

[jimbo B]

From jimbo B

I have a 1987 Wellcraft Nova XL 23 with a 260 hp Mercruiser - 350 chevy & high output exhaust. Engine sat idle for 3 years - only 300 hours. When I run it at 3600 rpm at 40 mph no visible oil leak. When I crank it up to 4400-4500 rpm the engine leaks oil quickly, but I can't see it because I need to drive the boat. Oil must somehow get on fan belt because it gets slung up to the underside of the engine cover and to the bilge area. In a 6 hour day, will lose a quart of oil. When idling no leak. Any ideas about where this oil may be leaking from? Maybe at the point where the fuel pump connects to the engine? Maybe at the front side of the oil pan? From behind the flywheel? Seems like the left side below the motor has more oil on the floor than anywhere. Confused.

 

[Don S]

Re: Merc 260 HP Oil Leak

Clean it all up, then spray the front of the motor with talcum power spray. Then run the engine at rpm for only a few minutes and see where the oil is starting from. You may have to do this several time and increasing the time to actually see where it starts from.
Everything on the front of the engine with a seal is suspect. Pan gasket, front crankshaft seal, tin timing cover with a pinhole.

 

[Bondo]

Re: Merc 260 HP Oil Leak

Ayuh,... Welcome Aboard,.... 'n to add to what Don says,...

The Highest point ya find oil, is very close to, or At the leak....

Like water, oil flows Downhill...