Oil in combustion chamber

bwjimbo

Recruit
Joined
Mar 10, 2013
Messages
1
I have what I believe is a 1990 3 cyl Yamaha 40ELD Precision Blend Ser#6H4 L 419175. It has been stored on my boat in my driveway for at least 6 months. I noticed oil leaking from a drain hole on the upper half. When I tried starting it, it wouldn't crank. I removed the top spark plug which was fouled with oil, and then I tried cranking it. It spit out oil. I returned the spark plug and it started right up, but with quite a bit of smoke. I took a spin on the bay, but I didn't feel like it was running smooth. What's the problem? What should I do about it? New here, and need some help...
 

Capt Ken

Commander
Joined
Jul 30, 2002
Messages
2,269
Re: Oil in combustion chamber

I don't believe that year had check valves in the oil injection lines. Without them, the oil can seep into the intake. Newer engines had the check valves. You can be sure by following the lines from the pump to the intake. If there isn't a small plastic piece inline, then no valve. If there is check valves, they need replacing.
 
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