your not going to find any hp in plugs...i guess if you gap 'em big and index them,,,maybe a few!....but on a stock engine w/low CR......not....O, NGK is the better plug of the two...merc has even changed to them.

Thanks for your reply Audacity. The only reason I switched to NGK, is that, my dealer said the exact same thing you said about Mercruiser. Not looking for any extra power, lookin' to be more effeicent.

you or your engine to be more effeicent??? you will not find that in a plug either...have fun out there!