Reply To: Compression for 1958 Johnson Super Seahorse

[John Mashl]

Dave,

Thanks for the info.  I don’t think I touched the choke or throttle before checking the compression so I don’t know what position they were in.  My compression tester does have a valve on the motor end.  I didn’t disconnect the compression relief valves.  I saw them but didn’t realize what they were.  (The last time I played with old outboards I was a teenager working on mid ‘60s 18 hp Evinrudes.)

All the wiring and fuel lines appear to be connected and in fair condition.  I asked a local outboard shop about what spark plugs to run at my elevation.  (I’m at 7,000’ in Colorado.  Some mountain lakes are higher.)  I believe they said to run a little hotter plug.  He sold me some Champion J8Cs.  I also plan to lean the air/fuel mixture using the carburetor’s slow & high speed adjustments to compensate for the less dense air.

I have the starter solenoid boxes and the wiring harnesses for both motors.  The solenoids work ok.  I can get ethanol-free gas.  In the 60’s we used to call lead-free gas “white gas.”  Now it’s all lead-free.  Good tip on the 24 to 1 for the gas/oil mix.

What spark plug would you recommend?   Champion J8C?  I think one motor had J4C plugs (the Indiana motor?)

I’ll try checking the compression using the electric starter.   Then I’ll try getting them running and check the compression again.

Thanks again.

John