Problem with fouled plugs on '59 Johnson 18hp

[asdasc]

Hi guys,
My old reliable 18hp is starting to have issues fouling plugs. I am running JC8 plugs in it. When I clean them up, it runs great for a weekend or two, then starts having issues. It is on a heavy pontoon boat, so probably heavily bogged down at times, but I rarely run it wide open anyway.

Would you suggest another plug? Or is it more in the carb adjustments? I have always run it with 25:1 TCW3 mix, but recently leaned that out to about 33:1. That doesn't seem to make a difference.

Both plugs seem to get fouled about the same time.

 

[kfa4303]

Re: Problem with fouled plugs on '59 Johnson 18hp

Hi asdasc. Great old motor you got there. I'm surprised that the plugs are fouling considering you're running J8C plugs, which are a bit hotter than stock, but make sense for low speed/trolling applications. 24:1 mix is appropriate for that year as well. I wouldn't go much leaner than that though. I would focus more on the carb, or the intensity of the ignition. If the spark can jump a 1/4" gap, then it should be sufficiently hot, which just leaves the carb. When was the last time it was cleaned/rebuilt? Probably wouldn't hurt to take a look. You may also want/need to adjust the hi/lo speed needles a bit. I would also try to run the motor at WOT once and a while to get it up to temp and burn off some excess fuel/oil. You may also consider doing a decarb procedure on the motor using a product like SeaFoam or Deep Creep. Here are some handy links. Good luck keep us posted.

http://www.leeroysramblings.com/johnson_E-FD_15_18hp.html

http://forums.iboats.com/showthread.php?t=167352

http://www.marineengine.com/parts/v...ntage-evinrude-johnson/377807/37780700001.htm

 

[asdasc]

Re: Problem with fouled plugs on '59 Johnson 18hp

Thanks for the tips! I am just heading out to the island for the weekend and will look into these. The carb hasn't been rebuilt in a few years, but that would have to wait until I pull it for the season.

Thanks again,