Right Spark Plug for a 1980, 2HP Johnson

Before buying a new spark plug, I Googled to find which one to use on a 1980 2hp Johnson Seahorse, model J2RCSM, problem is I get different numbers coming up, so how do I know which one is the right one or the best one , and why is it best?, Most say use Champion or NGK, but the numbers vary from a Champion J4C, J4J, J6J, J6C, RJ6C, or NGK, B6S, BR6S, B6HS, of course there are others, but those seem to be the most frequent. MarineEngine.com says they recommend a Champion J6J, but the Champion plugs they list for sale is a J6C,or a RJ6C, so I don't know what to believe! all I know about spark plugs is some have shorter thread than others, Does anyone know what number they came with when new, should I stick with that or go with something different, and why?. Very complicated decision for such a small item, but don't want to do damage by using wrong one, the one in it when I got it was an old NGK BS6, which may/may not be why its hard to start and runs rough. Any help is appreciated, Thanks

Use a J6C or the equivalent of that for best results.------Will spark jump a gap of 1/4" with ease ?---If it does not then the magneto needs attention.

racerone said:

Use a J6C or the equivalent of that for best results.------Will spark jump a gap of 1/4" with ease ?---If it does not then the magneto needs attention.

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Thanks, is there a peticular reason you say use a J6C instead one of the many other numbers.

Brand of sparkplug is not that important.-------Your motor would run just fine with a ------J6C---- installed with a magneto that is in good working order!

I need to correct my original post, the plug that came in the motor was an old NGK B6HS, not a BS6, I just got it mixed up with another plug I had. But notice the B6HS has a longer threaded part than other plugs, like the Champion J6C, could that be a problem with how it runs, don't know why some are short and some long, but as happens I have a new B6HS that I never used from another motor, if the motor runs okay with it, is it safe to use long term, considering its longer, so therefore the electrode will be farther into the cylinder than say a J6C?

Not sure why you are hesitating here.-----------------Champion J6C -----------------is the correct sparkplug !!

Not hesitating per say, but, before going to buy a plug, just checking to see what people have to say about it, because as I said in my original post, there are so many different spark plugs that are said to be the "correct" one to use. So I mean, other than price, Whats the diff between a Champion J6C and a J6J? I don't know! so I am asking questions, I am not a mechanic. I probably will buy the J6C for $5, if they have one, but what if they don't? do I order one and wait, or use adifferent one, and if that's the case, then why not just use the different anyways, especially if its cheaper.