Plug numbers: Which should I use?

[Big Al1]

I was going to replace the plugs in my Merc60 6hp, 1964 model, and the current plugs are Champion CJ6 I beleive. The manual says CJ7. Are the numbers temperature related? Do you think that Mercury updated the plug recommendations? Does the 6 rating run lower temperature or something? My plugs always seem wet like not all of the fuel is getting burnt. I have rebuilt carb and fuel pump and lines.

 

[Jack Shellac]

Re: Plug numbers: Which should I use?

Your best bet is to always use the plug recommended in the manual unless you have a special situation. For example, if you do a lot of trolling, use a hotter plug to keep fouling down. The plug in the manual is for all-around average use.