'68 Johnsonn FD-22M Compression Problem

[bassin'frog]

Rebuilt this motor and finally got around to checking the compression today.... unfortunately, I have 65 psi on the top and 105 on the bottom... Now, I know the readings should be within 10% of each other but my question is this, will the motor start? and if so, will the motor be alright? Or do I absolutely have to replace the rings in the top?

Bob

 

[nwcove]

Re: '68 Johnsonn FD-22M Compression Problem

when you say rebuilt, what do you mean? but the motor should start....as they will tend to seem to run ok on one cyl. id pull the head and have a look. it could be as simple as a $10 headgasket and a de-carb. jmo

 

[boobie]

Re: '68 Johnsonn FD-22M Compression Problem

Agree with nwcove. To much difference in compression.

 

[bassin'frog]

Re: '68 Johnsonn FD-22M Compression Problem

When I got this motor, I opened up the powerhead, cleaned up crankcase and shaft, and cleaned and inspected pistons and cylinders. Everything looked good. I replaced the head gasket also. Will recheck torque on head bolts and try compression again.
Thanks guys!

 

[yorab]

Re: '68 Johnsonn FD-22M Compression Problem

I had a problem once with a compression guage not sealing. Absolute fundamental and simple mistake, but it had me quite perplexed for a while. Make sure your guage is working well.