Re: Completed the compression test on my '85 merc 260
 

So would that mean I am looking at a rebuild if that's what the leak down test showed? thx


Jim

Re: Completed the compression test on my '85 merc 260
 

Proof is in the leakdown test,i did my motor a few wks ago and my weakest cyl had 120 psi crank compression (after 10 cycles),80% leakdown!!!,best cyl had 10 % leakdown and was bumping 160 psi after 4 cycles of motor. Funny thing was boat ran ok,was 1/2 mph off normal speed and didn't have much blowby. When you did your compressioin test did the lower press cylinders take more turns/cycles of the motor to get to there max? If they did it is definately weak,leakdown test,post your results,Smitty

Re: Completed the compression test on my '85 merc 260
 

Or they rebuilt it, and got the ring gaps too wide. This pearl of wisdom comes from the blowby encountered after a friend rebuilt his engine back in high school. That car was liking driving around a oil geyser!

Michael

Re: Completed the compression test on my '85 merc 260
 

the blow by seen is a alot. there are 2 mr gasket breathers on the valve covers(one on each side. When I slow down to idle after a run and open the engine hatch it looks like a smokehouse.

Carb was rebuilt twice because after the first rebuilt it started flooding the engine after 10 min of run time.


The motor has a mild aftermarket cam which I thought it should be running higher than 4500 rpm.