'76 40HP Evinrude Compression

[Sunken Ship]

I have exactly 90psi on each cylinder. Is this the correct amount for this motor? Both plugs were removed during testing. Thanks.

 

[Sunken Ship]

Been digging around...it appears that 90 is OK-not great. 90 was cold and without putting anything in the cylinders before testing.

 

[nwcove]

be happy that it both cyls have the same #. it should run ok at 90 psi

 

[gm280]

I have the '76 40HP Johnson version of your engine and my compression numbers were 115psi. But that really isn't as important as them being within 10% to 15% of each other. So 90psi can work without issue. You really have no idea if your compression tester is read properly or not. JMHO!

 

[Sunken Ship]

Thanks for the comments guys. I remember testing it back in '99 and it seems that it was closer to GM280's numbers. When I initially saw 90 I was sure worried! GM- I certainly do not have much faith in the compressor tester from Harbor Freight, but as you both said the two are perfectly even.

I really like this old engine. I have had it for so long I would hate to see it go down permanently over something major. I would probably re-ring it though.

GM- I just took a look at your motor. The only difference I see in the our motors is the color. Good to see another one still on the water!