On true speedboats they dont use bottom paints. It makes
it look cheap and also creates a drag, lowering the speed.

If you are talking run of the mill 60mph boats, I dont think that
it would be much of a problem. Worst case is to paint it
twice initially in the season for that extra protection.

I'd really be ****ed if I would have to pay someone later
on to blast the bottom because I used the wrong paint
for the job.