What year is my motor,and spark plugs question

Bought a 20HP johnson short leg motor today,cant quite figure the year it is,On the little plate theres them numbers,,J20CRCNB and also C8144052,,man behind the counter says its an 1981,previous owner doesnt have a clue,,looked up the "introduces "system,but there aint no B in there.Motor runs pretty decent except when in neutral there it sputters farts and coughs,bur when in gear either forward or reverse it runs just fine,,plug on it are ngks,,been told time and time again them engines run way better on champion plugs,,will put them in tomorrow,,thing is on the motor it says the plugs should be QL77J4,,can only find QL77JC4 out here,,wonder if they are different wondering what the C stands for?? Thanks for any help I might get on my just wondering what the ehhh..
Mike Redmond,from the north shores of the seaway in la Belle Province

Year is 'CN' or 1982, the B is a mid-year model change. Regardless of what a manual may say, (like 0.028"), OMC changed the gap on all plugs to be 0.030" and the C = copper cored electrode.

I can add that the "CR" part denotes "Canada Derated - Rope Start". I'd look into what they mean by 'derated', might be an easy performance gain to be had there. Or maybe it's really a 25 but with a 20 on the cover! :shock:

cliff58 said:

I can add that the "CR" part denotes "Canada Derated - Rope Start". I'd look into what they mean by 'derated', might be an easy performance gain to be had there. Or maybe it's really a 25 but with a 20 on the cover! :shock:

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Back in the day.. 20's were a very common motor.. The only difference to a 25 would probably be the carburetor. I had a 1981 Johnson 20 once upon a time.. They are nice and easy to find parts for as that model spans a lot of years.. Also any motor 20,25,30,35 is basically the same during that vintage.