Sooty spark plugs

A

aclam

Recruit
Joined
Jul 22, 2009
Messages
3
I have a 1999 Evenrude 90 fitch - all 4 plugs are very badly sooted up, she sounds like she is missing on just 1 cylinder through out the rev range.
Any ideas what is causing the carbon, could it be the choke is not coming fully off?
 
S

seahorse5

Rear Admiral
Joined
Jan 24, 2002
Messages
4,698
Re: Sooty spark plugs

Soot covered plugs on an older FICHT motor is normal. At high speeds they clean off and are usually a nice tan, but as soon as the motor slows down below about 1800rpm, the combustion process changes to the lean burn mode and the plugs will soot up.
 
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