I actually broke off a thruhull right at the interior
nut. Fortunately there were two of us! We were attempting to remove the valve from the thruhull to replace it. We also had wooden plugs handy. The thruhull and valve were both very corroded...electrocorrosion. It was a 2 inch thruhull, drain for my holding tank
. It's pretty scary to see the water
pouring in!! Anyway my compadre just put his foot over the hole while I grabbed the bung and hammer and handed it to him. It worked well. We then took our time and got together all of the stuff we needed for a repair and fixed it the next day with a new thruhull and valve. We did the repair in the water
and managed it without problem.
But...I'm now worried about all of my "seacocks". Actually, mine are all thruhulls with valves. I'll replace them all next spring when I haul out
and will be following MaineSail's advice/instructions on thruhull replacement. It'll probably be about $1000 just for all of the parts!