Johnson 50hp '82, running rough

manifestation: after running fine on 2 outings, the day started out running fine. 15 minutes later, after I hit the throttle entering Pleasant bay from little Pleasant bay I hit a couple of bumpy waves. The engine started running at less than 1/2 speed, running rough. Same at idle: very rough, stalling, the idle lever made little difference in engine speed.
evidence that I should have given credence to: lower carburetor had a little gas dripping out the air intake.
tests: fuel bulb seemed to pump up fine. But it slowly got un-firm. Pumping it while underway made no difference; removing either plug wire caused stall; plugs looked OK. similar to each other; compression was good, same on both cylinders

Anonymous