I get several small omc outboards to work on each boating season, It seems that the omc 9.9 is the only one I see that uses the perma-gap type plugs L77 or L87v The ignition system seems to be for the most part identical to the 15 hp, looked on the Evinrude / Jonny .com & they do call for this type of plug, was wondering if anyone knows why? thanks