Johnson seahorse 140 V4 compression question

[Tyrrell- Doug Latham]

I just bought a boat and motor off a guy. I took it home and did a compression test and all cylinders were at 90 psi. Is this normal or am I in trouble? I think the motor is a 1985.

 

[Tyrrell- Doug Latham]

I looked up VIN. its a 1981..any help?

 

[racerone]

The most important fact is that the compression is even.------Possibly your gauge is reading low.------------And NO you do not need to have throttle wide open to do this test !

 

[Tyrrell- Doug Latham]

Brand new gauge I bought today but that doesnt mean anything. I redid test one actually might be at around 81 or 82. I read where the 1981 seahorse 140 was a low compression motor? Any help on this?

 

[racerone]

Some motors may have had thicker head gaskets installed to lower the compression.----Might be worth while to remove the bypass cover ( 6 -1/4" bolts ) to inspect piston and rings from the side. Will cost you a 99 cent gasket and worth doing.

 

[Tyrrell- Doug Latham]

How much speed should I get out of that motor with it mounted to a 1966 sea ray 190 srv and 90psi compression