1974 Evinrude 25Hp Plug Question

Looking at my service manual, it specifies Champion UJ4J plugs. Looking for the plugs I see several alternate replacements. Is there a particular plug anyone has found to be best that replaced the original?

I have replaced them with others and have gone back to the stock plugs. Seem to work better for me.


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By "alternate" Do you mean brand, manufacturer, heat range, electrode material etc?


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Both brand and heat range. I had a 20 that didn't want to idle/troll very long without loading up and fouling. The previous owner had selected ngk in a higher heat range. I read up on the subject and put a pair of 4J's in it and presto, it ran great. It's unexplainable to me but others have had similar experiences. Ngk makes a fine plug, and are in most of my small engines. But my johnnyrudes get factory spec plugs now.


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WALI4VR said:

By "alternate" Do you mean brand, manufacturer, heat range, electrode material etc?


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I was not finding those particular plugs just lists of alternate plugs. Maybe I have the wrong impression but I thought tbe plugs were no longer available.

I think it was j4c I ran but would have to go check.


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Sorry. It was j8c. Went out and looked to be sure.


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Weldorthemagnificent said:

Sorry. It was j8c. Went out and looked to be sure.


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I appreciate it. Thank you.