1991 40 hp bad spark update

MudLake

Seaman
Joined
Nov 18, 2009
Messages
65
Tones sometime go away. thats good

Took boat out on water and had carb or spark failure.

Came home and soaked carb in lacquer thinner the remove more varnish deposits. started it up in a barrel.

Maybe not a carb problem.
Hard to determine if spark or carb issue. However today i started it up and concluded it has a weak or Intermittent spark on bottom cylinder.

Interchanged the plugs no difference.
interchanged plug wires no difference.

Pulled top spark plug wire off while running motor stalled.
Pulled bottom spark plug wire of while running and motor kept running on one cylinder.
Bottom spark does not jump as far as top stark and is also intermittent.

Conclusion: bad spark circuit for bottom

Where do I go from here??
What to check or even change first?

cheers
 

Daviet

Fleet Admiral
Joined
Sep 24, 2008
Messages
8,958
Re: 1991 40 hp bad spark update

I would'nt change anything until I got the OEM manual and used the troubleshooting section to locate the problem. You can throw all kinds of parts at it and still not fix it. Get the manual and fix it right the first time.
 

tashasdaddy

Honorary Moderator Emeritus
Joined
Nov 11, 2005
Messages
51,019
Re: 1991 40 hp bad spark update

swap the coils, then test again. if weak spark follows coil. replace coil.

By the way that is a great motor.
 
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