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20 hp Johnson Outboard Spark plug help


moemoe

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Hi guys, I have a question for you, I am going to to my wifes family's cottage this weekend and they have a motor, a 20 hp Johsnon that hasn't been run yet this year, I was hoping to bring up some new plugs for it, anyone know the model of plugs? I know, I know, noone knows the exact year but my guess would be late 80's to early 90's, Thanks!

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Both Champion QL77JC4 and QL82C are fine. The former was the original recommendation. I don't know if they changed to the hotter QL82 after they dropped the oiling ratio back down to 50:1 from 100:1 or not, but if you do a lot of trolling I'd get the QL82's. If you do more WOT running then perhaps the QL77 is best. Either is fine. Plug gap is .030".

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A question, and honestly I don't know, but how do you know that the QL82's run hotter and why is that better for trolling? Because I do like to troll

 

For Champion plugs (like most, but not all spark plugs), The higher the number (in this case 77 vs 82) the hotter the plug.

Edited by boatman
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