Johnson 115 Spark Plug Read

FishHunt23

Seaman
Joined
Jan 4, 2007
Messages
50
I recently purchased a 1998 Johnson 115 FastStrike (J115GLECM). It runs fine, and the previous owner said he had no problems with it. I pulled the spark plugs today for the first time and found that the plugs in the two starboard starboard cylinders look much different than the plugs from the two port side cylinders. I have attached a pic for reference. The plugs from the starboard side have darker ceramic and a light colored ground. The port side plugs have white ceramic and "normal" looking grounds. There's obviously something different between the two sides. What should I be concerned about/looking for? Thanks for the help.
 

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boobie

Supreme Mariner
Joined
Nov 5, 2009
Messages
20,826
Re: Johnson 115 Spark Plug Read

The only way to take a correct plug reading is to run the mtr at wot and immediatly shut it off. Then pull the plugs and see what they look like.
 

FishHunt23

Seaman
Joined
Jan 4, 2007
Messages
50
Re: Johnson 115 Spark Plug Read

I get that, but with the plugs looking so different between the two sides of the block there is obviously something different between them...
 

Faztbullet

Supreme Mariner
Joined
Mar 2, 2008
Messages
15,589
Re: Johnson 115 Spark Plug Read

Looks like running lean on that side, could be a reed manifold gasket leaking or the t-stat is stuck open on port side causing incomplete combustion.
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
27,033
Re: Johnson 115 Spark Plug Read

The darker ones are normal. The lighter ones may be overheating or nearly overheating or running lean.
 
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