clarification on my plugs

[RNyachtclub]

I need some spark plug clarification, my motor says J4J I understand they do not make that any more so I got some J4C's and gapped them the boat ran good cut out once in a while but not the point of this post. I looked around on here to see if there were any other plugs I should try I found some suggestions of a J6C. I have not run it with these plugs yet in the process of fixing some ignition stuff... I went to my local marine store today and got talking with the guy behind the counter he said to run a J8C. This seems to hot but maybe I?m wrong I just need some clarification. The motor is a 1965 18 hp evinrude fastwin.

Also when I ran it a while ago I read the plugs a couple times I noticed there was no color on the tip it seemed to rich like the fuel was washing them clean. They were a hair wet with a hint of brown but you could wipe the color off and it was silver again. My question is should there be the cardboard brown color carbon on the tip I?m looking for or do these old two strokes run rich to help keep them cool??? Or is this because im not runnuing a hot enough plug, or my carb setting are way to rich...

i can give any more info if needed. Thanks.

 

[Chinewalker]

Re: clarification on my plugs

If the plug is wet and can be wiped clean, you may have a misfiring plug. Could be a result of weak spark. Check your ignition components, point gap, etc. Ideally, they should be a dry, light brown and it shouldn't come off without the aid of a wire brush...

I run J6Cs in most of my older Johnrudes, but am not opposed to the J4Cs. I just find the J6Cs foul less easily with the fat oil mixes I run. J8Cs are too hot...

 

[JB]

Re: clarification on my plugs

J4C is the "correct" plug, gapped at .030". I think it works best for high speed running. If you do a lot of low speed trolling J6Cs work a little better. Your instinct is correct, the J8C is too hot for that engine. It is a lawnmower plug.

It is very common for plugs to get wet with fuel in the short time between the spark being shut off and the engine actually stopping.

 

[HighTrim]

Re: clarification on my plugs

I agree with Scott, I run J6Cs in almost all of my 50s 60s Johnny Rudes. It is a great all round plug.

I collect all the NOS J6J and J4J plugs I can find, but they are getting rare.

 

[nwcove]

Re: clarification on my plugs

jmo, but not much point to "read" the plugs until you get your ignition system work done. i prefer to run the j6's tho, as most of my running is putt putt, with a bit of wot thrown in to blow the crud out now and then.