Have been running my first boat for a few months and just fitted a new piston and rings. It had about 12hrs running time on good oil. Engine is moderately ported, piston lightened etc. No obvious wear, although the new wrist pin bearing felt a bit tighter than the old. Is this too often to re-build, and what normally fails first in these engines?

On my primary RACE engines that get run a lot !! have original pistons in them many times for 3-4 seasons running doing a re-ring maybe once if ring shows clipping around ex port ?

Good oil, not put away end of day wet inside .... 100's or hours running between service intervals is not uncommon.

Thanks Scott, sounds like I'm way too keen, and no doubt your engines are going harder than mine. Have been used to my sons 4 stroke dirt bikes. If you get a 250cc 4 stroke up to 38hp, (32hp stock), an engine is good for about 12 hrs between re-builds,(down from of 40hrs stock). I just assumed that with all of those big holes in the walls and a massive power output per CC, these small engines would die quickly.