Broken thru-hull
Are you talking about the ball valve, or are you really talking about the thru-hull. Is the boat in the water? If the thru-hull is actually broken, the boat will need to be hauled out to be replaced. If you are talking about the ball valve that is attached to the thru-hull, here is how I replaced the same one on my 93 C36. In the water, go under and place a suction cup (what works great is one of those handles with two suction cups, one will hold the other over the opening) over the opening, or a small chunk of clay. Don't push it up into the thru-hull just try to get it to stick. Using two sets of water pump pliers, use one to maintain the position of the nut on the thru-hull. Use the other to unscrew the ball valve. Clean the teflon tape from the thru-hull, and apply new teflon tape, at least two layers, then screw the new ball valve back on. Did the handle break off? I have replaced every one on my boat, two for broken handles, and two were just getting very hard to open, or close. The manufacturer says to lube twice a year, (who can do that). I have not had any problems with the replacements (yet), and one is over four years old. Hope this helps.Mike McCann C36 1227