Boatyard launched the boat and galley sink seacock was leaking. I tightened locknut but it didn't help. This is a bronze seacock on a Bristol 31 1983. I read somewhere that there is someway that these can be dismantled and reseated using some sort of pumice. Any ideas?
Yep, that's it. You could jump in and put a plug in the thru hull while working on the seacock. I was able to get 4 out of 5 seacocks on my Bristol to seal. Don't change them unless you have to, they are very good seacocks.