Reply To: 57 Johnson 7 1/2 Starts but won’t run

[Don]

JohnRude wrote:

Thanks for the suggestions. For added measure, I’ll make sure the connection holes from/to the tank are clean. I already replace fuel line and air line hose.

Correct about the shear pin. It was missing entirely. I didn’t check the lower unit at all except to change the oil before working on the top end. The old oil was dark and stormy but I’ve seen worse.

I’m starting a new thread about another mysterious problem.

Just to be clear, this engine needs to be mixed at 16:1, regardless of the oil used.  True, oils have improved over the years, but not all that much.  This engine uses “plain bearings” on the large rod/crank ends and requires plenty of lubrication, or the crankcase will ventilate as pieces of the rod blow through it.  When in proper tune, these engines barely smoke at all, even at 16:1.  I realize that even some of the OMC literature states these plain bearing engines can be mixed at 24:1, ignore that.