Plugs fouled up

Warpath42

Recruit
Joined
Jun 28, 2008
Messages
3
I have previously posted about my motor problems.
http://forums.iboats.com/showthread.php?t=262638
I have two 18 HP Johnson motors, a 61 and 65. The 65 developed a problem so I bought the 61. I didnt realize the two are supposed to use different fuel mixtures. The 61 using twice the oil of the 65. I took my boat out and the motor ran well using the incorrect mixture. I went out a week later and had problems. After only ten minutes or so of full speed it lost a lot of power. I pulled over and fished thirty to forty minutes. When I started back up it still did not seem to have full power. I ran it maybe another ten minutes at the most. As I pulled in to another fishing spot it died on me. Fished awhile and was unable to get motor started back again. I posted about this and was told the mix was probably not the culprit. I finally got a chance today to start checking the motor over. Pulled the cowl off and right away noticed oil stain around both spark plugs. Plugs were tight enough I couldn't remove by just my fingers. On removal both plugs were fouled with oil. I cleaned them up with starting fluid to remove the oil. Then cleaned with a small wire brush and put them back in. I actually waited for the starter fluid to dry up before putting them back in. I then tried starting the motor. After about eight pulls on the rope I pulled choke out and it almost started. Pushed choke in and pulled. Started right up. I ran it for fifteen to twenty minutes solid. Was able to switch in and out of forward and reverse and keep it running at slowest neutral speed. Pulled fuel line off and ran for about two minutes till it died. I pulled the spark plugs and they looked fine, no fouling. Plugs are champion J6. I should mention I did pull the plugs and clean them before I took the boat out the first time. Did not pull them between first and second time, about a week.
I dont understand why the plugs fouled so badly. The fuel mix was actually lean right? There shouldn't have been excess oil. Could my plugs have not been tight enough, and this caused an oil build up? I want to take this motor to a mechanic to get it in top shape, but I don't want any excess charges or time delays due to simple problems I could take care of my self.
Any suggestion or insight would be appreciated.
 

F_R

Supreme Mariner
Joined
Jul 7, 2006
Messages
28,226
Re: Plugs fouled up

Lessee, help me out here. Does the motor in question have an adjustable high speed jet? Was it set correctly?

You could have a lot of loose carbon in the cylinder head that came breaking loose at high speed and lodged in the plugs. There are lots of de-carboning potions on the market, but frankly I would pull the head and clean it out and be done with it. Use a new gasket, properly torqued to reinstall.

Your plugs may have been loose, if not now, maybe in the past. Or the gaskets on them are hopelessly shot. Loose plugs will run hot (the plug ceramic is hot) but that would reduce fouling, not increase it.

The other possibility is you may have bad coils in the magneto. Very common. The fix is to replace them.
 
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