spark plugs.....cj 6's, vs cj 8"s

[nwcove]

are cj 8"s too hot for my 1962 3hp lightwin? (couldnt get cj 6's but dont want to kill the little motor)

thanks

 

[oldcatamount]

Re: spark plugs.....cj 6's, vs cj 8"s

CJ8 is the recommended plug (I think) and the gap is .030. Check here at Iboats Marine Store.

 

[nwcove]

Re: spark plugs.....cj 6's, vs cj 8"s

thanks oldcat! the plugs that were in it were 6"s, ...and i forgot to gap them. couldnt find any reference info at the marine store. will have to do some more looking, just to confirm.

 

[hidef]

Re: spark plugs.....cj 6's, vs cj 8"s

Gap them .030 and they will be fine. They are a little hotter than the J6 plug but they won't foul out from the 24:1 oil/gas mix as easy if you are doing a lot of trolling. I am surprised your Canadian Tire down there doesn't stock them. They had to go into the back room for my J6 plugs.

 

[kfa4303]

Re: spark plugs.....cj 6's, vs cj 8"s

While J8C does seem pretty hot, I think they probably use them b/c 3hp motors are often used to troll with, so they wanted to be sure they burned all the fuel even at lower rpms. Just a guess.

 

[nwcove]

Re: spark plugs.....cj 6's, vs cj 8"s

thanks guys, (went to napa....they didnt have them, but if the 8's are safe, they should actually work better in the cold salt water!)

 

[lindy46]

Re: spark plugs.....cj 6's, vs cj 8"s

I use J6C's in mine and can troll all day without fouling. And I use a 16:1 gasil mix.

 

[jbjennings]

Re: spark plugs.....cj 6's, vs cj 8"s

Do you mean J6C's? Those are correct. jc8's are NOT correct--pretty much lawn mower plugs and are much too hot.
JMO,
JBJ

 

[Tim Frank]

Re: spark plugs.....cj 6's, vs cj 8"s

CJ6
Is this a typo?
As JBJ says, correct plug is J6C, gapped at .030".

CJ6 is the plug I use in an air-cooled B&S driven Toro shredder.

 

[kfa4303]

Re: spark plugs.....cj 6's, vs cj 8"s

I think J8C seems too hot too, my 20 hp uses J8C.?.? but the iboats store page says Champion J8C for 3 hp of that vintage :/ Go figure. I would go with the cooler J6C just to be safe.


http://www.iboats.com/Johnson-Champ...7681945--**********.701782496--view_id.669920

 

[Daviet]

Re: spark plugs.....cj 6's, vs cj 8"s

My vote goes for the J6C also.

 

[JB]

Re: spark plugs.....cj 6's, vs cj 8"s

J8C is too hot for that engine. That is a lawnmower and antique chainsaw plug.

J6C is the "correct" plug, but I would run J4C unless I was doing a lot of trolling. OMC specified J4J (now J4C) for that outboard in their 1964 Service manual

The "correct" gap is .030", but at various times OMC suggested .040" to minimize fouling if operated at low speeds a lot.

The problem is the lousy, incorrect charts made up by Champion, not OMC or BRP. There are a lot of errors there.

 

[kfa4303]

Re: spark plugs.....cj 6's, vs cj 8"s

Thanks for the clarification JB. Do you think I should stick with the J8Cs in my '66 20 hp, or should I go to J6C also. I believe my old '66 33 hp used J6C come to think of it, so it makes sense that the 20 hp would too. Any thoughts? Thanks.

 

[194269]

Re: spark plugs.....cj 6's, vs cj 8"s

Please run 16:1 fuel mix in your 3hp, its an all bushing engine. And the next question your 20 hp should have J4C in it as well as the old 33.

 

[nwcove]

Re: spark plugs.....cj 6's, vs cj 8"s

the motor was given to me with cj-6 champion plugs installed, couldnt get the 6"s. so went with the cj 8's? so both of those plugs are wrong for that engine? great info!
(on the plug topic, (have posted another thread), what would cause an engine to go through plugs like no tomorrow.....oldish points and coil setup??)

 

[nwcove]

Re: spark plugs.....cj 6's, vs cj 8"s

J8C is too hot for that engine. That is a lawnmower and antique chainsaw plug.

J6C is the "correct" plug, but I would run J4C unless I was doing a lot of trolling. OMC specified J4J (now J4C) for that outboard in their 1964 Service manual

The "correct" gap is .030", but at various times OMC suggested .040" to minimize fouling if operated at low speeds a lot.

The problem is the lousy, incorrect charts made up by Champion, not OMC or BRP. There are a lot of errors there.

numbers on the plugs are....as installed, not run other than in a barrel, are cj-8, im really confused with the "j8c" as compared to "jc8" ?

 

[hidef]

Re: spark plugs.....cj 6's, vs cj 8"s

CJ 8 is not the correct plug you want either the J4C, J6C or J8C. The CJ6 is a lawnmower plug where as the J6C is an outboard plug. Canadian tire carries the J6C you will have to ask for them at the parts counter.

 

[Tim Frank]

Re: spark plugs.....cj 6's, vs cj 8"s

numbers on the plugs are....as installed, not run other than in a barrel, are cj-8, im really confused with the "j8c" as compared to "jc8" ?

To simplify,
1) You should not be running "C" series Champion plugs in an outboard motor whether CJ6, CJ8...or whatever.
2) J8C is a common Champion number when dealing with older OMC O/Bs.
3) JC8 is not a Champion designation/number at all.

 

[nwcove]

Re: spark plugs.....cj 6's, vs cj 8"s

thank everyone, the motor was given to me with cj6's , but am glad to find out the right plug for it! it looks like its been through a war, but still has 90psi compression top and bottom, so its worth looking after.