1972 Johnson 20 hp

Action · Jul 18, 2014

I was given a 1972 Johnson 20 hp, It has been sitting for many years. Just wondering what the compression should be? High/low? I have done nothing to it yet but plugged in the compression tester. Pulled 3 times each cylinder, Both came in at 95. Seem low?
Thanks
Jack

SumDumGuy · Jul 18, 2014

Some will say that is low, but it would work for me. Especially since they, the cylinders, are close or even in pressure.
Shoot some fog oil in the cylinders, move it around and let it sit for the night. Then check your compression again for S&Gs.

Replace the impeller and check the lower unit oil and fire that thing up (at least try, then rebuild the carb).

Action · Jul 18, 2014

Thanks,
Think i will soak the cylinders for a couple days and try again. Have to repair a few wires (elect. start-kill switch) before I try to start it.
Thanks
Jack

Charger25 · Jul 19, 2014

IMHO 95 psi is not bad for a 1972 motor. Like SumDumGuy said shoot some fuel mix in and it might go up

Action · Jul 20, 2014

Hooked up starter and spun it over a few times, hooked up compression tester. This time came in just under 120 in both.
Thanks

1972 Johnson 20 hp

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1972 Johnson 20 hp

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