I've read a few great posts on this site about proper installation of thru-hulls, seacocks, and ball values, particularly by Maine Sail. Thank you. So it sounds like capping a thru-hull with an NPT cap is a bad idea. Where can an NPS cap be obtained? I have a sound thru-hull in an extremely well protected location (zero possibility of anything whacking it) that is now unemployed after removal of a heat pump. I've also removed the NPT ball valve that was stuck on the thru-hull. I'm not quite ready to yank the thru-hull out of the boat altogether, so can an NPS cap be had for it?