Re: Late 50’s Johnson 18 hp compression?

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May 18, 2018 at 10:12 pm #76284
chris-p
Participant

    Forgot about your main question!

    Definitely the 18s are over 100 psi on a good motor. I have literally had hundreds of the 18s. Not uncommon for good ones to have over 120 psi.

    My GUESS is new they have around 140 psi. I have one motor that is almost NOS. Ran very little. It is a 1957 Evinrude 18hp. The bores still had original cross hatch. All I did was install new rings, at it was sitting at 140psi.