Reply To: 1960 Johnson 3 HP JW-16

[Don]

Don’t feel bad, happens to all of us. But, you do have to verify those compression readings….Needless to say, 18PSI is too low, especially after rebuilding. These engines have such small combustion chambers, minor differences in gage construction make big variations in readings. I would try a few more gages, one without a hose would be best. Be sure the gage is reading in units of PSI also. Hopefully, this is just a gage issue. If not, there is some sort of internal problem(s) causing a lack of compression….