I have a 1957 Johnson 18hp Sea Horse. I am trying to find out the gap for the spark plugs and the proper oil-fuel mixture for this motor. Can anyone please help?
Re: 1957 Johnson 18hp spark plug/oil fuel mix questions
manual says J4J for plug , I'd use J4C or J6C. if you do a lot of fast running gap at .030, if you do a lot of trolling gap at .040, cuts down on plug fouling. fuel oil mix is 24/1 . points gap is .020
Re: 1957 Johnson 18hp spark plug/oil fuel mix questions
The J4, J6 and J8 plugs are almost identical, only difference is heat range. J4 is coldest of the lot, J6 medium, and J8 a hotter plug. I sometimes run a J8 when I'm trolling alot and a J4/J6 when I'll be doing lots of traveling to get to stationary fishing spots. My FD 11 Johnson seems to thrive on any of the three.
