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Forgot to add oil but seems fine…???

N

newboatqld

New member
I've a rebuilt early 1990's Yamaha 85hp outboard - head unit rebuilt last year and runs beautifully since.

Yesterday I switched fuel pumps without adding the 50:1 oil mix and ran it pretty gently for approx 30mins before I realised. In that time, there were no dodgy sounds/power drops. After adding oil (25:1) it continued to work without any noticeable difference.

From what I've read, running with no oil should have caused serious issues within those initial 30mins. As I've only just recently moved from a 25:1 to 50:1 mix (I kept the mix high for first 20hrs post-rebuild), could there have been enough oil still in the motor to help negate my dumb mistake? Feel I'm clutching at straws and am worried that sometime soon the engine'll bite back and can't afford for that to happen out at sea.

Any advise gratefully received. Thanks.
 
Do a compression test.------Motors will run for some time with the oil that is in the crankcase , without new oil coming in with the fuel.---------Compression test will give the answer.
 
My guess is that there was enough oil in the system to let you "dodge the bullet" this time. Yamahas are known for their ability to survive when others will not. Even a small decrease in compression is not a deal breaker. I would not be surprised that you were lucky.
 
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