Clunk!

[Xandre]

I have a 1968-69 33 HP Johnson Super Seahorse on a small 14 runabout which is making a "clunking" noise when in gear but with the throttle all the way down. When I'm cruising and have the throttle all the way open I don't hear any problems.

Any ideas what this clunk could be?

Thanks!

 

[F_R]

Re: Clunk!

You are probably hearing what is called a "lean sneeze" It is caused by the fuel/air mixture being too lean (not enough fuel for the amount of air that it is breathing). When it is too lean, the fuel catches afire in the crankcase, giving that ka-chunk sound. This only happens at idle speeds. Thumping at high speeds is something else. Try giving the carburetor's slow speed knob a tweak to the left, toward "rich". That should fix it.

 

[Xandre]

Re: Clunk!

I will try this today. I have never adjusted the knobs as I have been unsure of how they affect the engine.

Thank you for the prompt reply!

-Alex