68' johnson 20hp...which spark plug?

[Roy Wirebaugh]

I have a 68' johnson (fd 22m) 20hp. I need to know which spark plug to get. I have found 3 different plugs recommended for the motor and dont know which would be best. The 3 are j4j, j6c and j8c. Can anybody help me out?..Thanks, Roy

 

[Beek14]

Re: 68' johnson 20hp...which spark plug?

Stock spark plug for this outboard is J4J. Refer to http://www.boats.net/parts/search/BRP/JOHNSON/1968/FD-22A 1968/POWERHEAD GROUP/parts.html for my quote.

 

[samo_ott]

Re: 68' johnson 20hp...which spark plug?

I put J6C's in all my 50's and 60's outboards, but I don't troll (sp?). I go flat out.

 

[Roy Wirebaugh]

Re: 68' johnson 20hp...which spark plug?

What is the difference on trolling or not? The main lake we use is mostly no wake on on over half of it, so we are just barely above idle. Would the J8C be better or would this hurt the motor on the few times we go to the river to play?..... Roy

 

[royal0014]

Re: 68' johnson 20hp...which spark plug?

Cold plug vs hot plug. Basically, if you do a lot of slow speed (trolling), you want a hotter plug so it don't foul as easy. But if you run wot point to point, go cold plug.........

 

[Roy Wirebaugh]

Re: 68' johnson 20hp...which spark plug?

Thanks folks, I understand now. I think we will go with the J6C.... Roy

 

[Vic.S]

Re: 68' johnson 20hp...which spark plug?

J4C are the currently recommended plugs for the engine !

If you have trouble with fouling ( when trolling for example) give J6C a try.

They should be gapped at 0.030" although originally the gap was probably 0.040"
Use the gap that works best... if there is any discernible difference .