For my 1985 120hp Evinrude the manual says use Champion QL77JC4 for "Sustained Low Speed/Normal Operations" For an alternate spark plug they list L77JC4, but they don't say what it's for. Is this the one you'd use for better high speeds/waterskiing? Basically, what's the "Q" stand for and has anyone had better luck with an NGK? (Or have the cross/ref no. to NGK)? Thanks