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Compression test 1990 Johnson 70 HP

S

Sam2001

New member
I'm reading 105 PSI across all 3 cylinders on my 1990 Johnson 70 HP motor is this a fairly good reading for a motor this old ? Also this is the first time this motor has been turned over since 2002.
 
That 105 is enough that the engine would run if all else is as it should be. I assume the cylinders may be somewhat dry due to sitting for 15 years and will increase with a little lubrication/running.

Spark, with all s/plugs removed should jump a 7/16" air gap.

No doubt the carburetors will need a good cleaning/rebuilding as needed.

Keep us updated.
 
Thanks for the response ! The VRO pump was leaking pretty bad and the last owner had by passed it , so I'm thinking of converting it to a regular pump and mix my fuel is there after market fuel pumps out there ?
 
That's good compression number as this is the 56ci block. It has a idle relief hole in sleeve and that reduces cranking compression about 10psi....
 
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