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1985 Honda BF100 SA ( 10 hp ) low compression

G

Gbode

New member
Looking for some guidance please. My Little 10hp outboard actually runs and idles great, usually cranks right up on first pull. The issue is when I’m at full throttle on the water after about 30 seconds the motor will die out. I can crank it right back up and it’ll do it again. Thinking something may be going on with the compression and fuel pump, I checked the compression yesterday with the motor hot and throttle opened up and I’m only getting 70 psi per cylinder. I have no water in the oil or anything like that but could it still be a blown head gasket or do y’all think the rings are worn?
 
Hi,
I agree with you...that is very low compression.

But, if it starts and runs, not sure if that's why it is shutting off like that. I would not assume it has a bad head gasket right off the bat.

Yes, the rings could be badly worn but first I would check valve adjustment and timing making sure that the timing belt hasn't become loose due to age.

If you find that you need to make any adjustments and/or the belt needs replacing, that should improve the compression some.

If so, then you will just have to see if the engine will stay running or not after those repairs.

Good luck.
 
Thank you for the quick response. I’ll adjust the valves and see if it helps the compression. I just can’t believe the compression is so low. I mean it runs like a sewing machine, no hesitation, no rough idle and runs great full throttle until it dies out.
 
Yeah,
It always surprises me how good some of these run with compression under 100 psi. But 70 is really getting down there.

Does the engine die out like that when you run it with the hood off? These are also famous for having the exhaust pipe gasket fail and starving themselves of oxygen. But, take the hood off and... voila!...runs forever.
 
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