Re: New purchase, needs bottom paint, no trailer
My sink works as same... as long as the hose/sink is always above the waterline (significantly), having the sink drain below the waterline is fine. But like others said... if the seacock is frozen, and you start wrenching on it in the water, oh, that'd be a mess.
I've also read that there are several through hull seacock types. Some have a flange, and are surface mounted from below. Some have a flange and are counter-sunk but also surface mounted from below, a final type are surface mounted from inside, and flush mounted. The last type are a huge problem because as they fail, they basically break off easily from the hull, leaving you with a hole. I know of others from the Catalina 25 forum remarking that there was a few years Catalina did this on their trailerables, and they then changed how they installed them.
Either way, fixing that seacock should be done out of the water, and should be addressed as to the real problem (might be more than a stuck valve).
Hull #68 S2 7.9 on our little landlocked puddle, Lake Wallenpaupack, PA, it's cheap, trailerable, and paid for.