Big Twin Saw Sparks

[New_Era]

1970 Evinrude Big Twin 40 hp (40052A). Removed starter in order to remove carburetor. Noticed the screw in the hole circled below was stripped or wrong size. Just loose in the hole. Thought it didn't matter much since only impact would be on starter bracket. Fired up motor yesterday to decarb with SeaFoam and noticed spark deep in the hole. Shut off and found a screw with similar threads and closed the hole. What was I seeing? Is this the manifold or part of cylinder.

Thanks,

Ron

 

[F_R]

Re: Big Twin Saw Sparks

Well, that brings up the next question: Does that hole go clear through into the crankcase? I'm suspecting that it does. That could cause a condition called "lean sneeze", or coughing due to too little fuel or too much air. Too much air would be a logical conclusion with the hole open.

Anyhow, lean sneeze is the fuel/air mixture catching fire in the crankcase. That obviously is what you are seeing. Put the screw back in.

 

[New_Era]

Re: Big Twin Saw Sparks

F_R,

I think you are absolutely right. Last time I took boat out it would die when I throttled back to idle in gear. It didn't do anything that I would describe as "sneezing", just would die. Yesterday, with the improvised screw in place it idled fine in gear. Thanks again.

Ron