[tytoolbelt]

I'm new with motors in general. Never done a compression check. Is there a Compression 101 thread on here somewhere. I am looking at a rebuilt 140hp Evinrude with (what he says) has 10 hours on it. Everything looks rebuilt and new. What should the compression be? I've read and it sounds like 120 to 130 psi. Is this correct? How exactly do I go about doing one of these checks? Both plugs out? One plug out? I do know from reading that it should be a warm engine when doing it.

Thanks in advance for all responses.

Ty

[Dhadley]

As long as it's even, no less than 15 lbs difference between high & low. 120 to 130 may be a bit high for that motor. You can try it with all the plugs out but on loopers you may have to take out 1 at a time. Just try it and see. make sure you have a good charge on the battery. No matter how you do it, do it the same every time.

[flabum]

Depends on the year of the motor. The older crossflow 140's will get upward 120 - 130 on a compression test, the loopers are generally lower. As long as the highest and lowest readings are within 15% (as staed earlier) you should be good. If the motor is a loop 140 ('87 or newer), the the heads may have been shaved some and you will need to run higher octane fuel to keep it happy.

[ezeke]

I think that the last TRL 140HP is 1983 which makes them (TRL) all crossflows. If the rings and cylinders are in good shape and you test with all the plugs out, you should be in your range if you are at sea level or near it.

[tytoolbelt]

Thanks guys. I will go get a tester and test it out.