Others can probably tell you the difference in these mags better than myself but I'm just curious why you're not considering a high output electronic like MSD, Crane, or others. If this is a recreational type boat that see's alot of "idle time" they run much cleaner (more spark at low rpm) and keep you from continually loading the plugs up. Mags work great at more rpm but they use a little horsepower up too. Just thought I'd throw that out for discussion.