Through Hull Inspection

Tommy Bahama · Post by **Tommy Bahama** » Sun Oct 16, 2005 5:15 pm

Well, the sea-cock maintenance seems to be pretty well covered but since my boat is out of the water I would like some inspection advice for the through hulls.

Mine (all 3) are bronze and the sea-cocks appear to be fairly new. The through hulls "look" fine but is there any criteria for proving that? I ask, because my bronze rudder gugeon "looked" fine but started crumbling like pottery when I gently attempted to remove it for rudder repairs. The through hulls are flush to the hull and threaded on the outside. I don't see any evidence of through bolts like I've seen in some catalogs, so I'm assuming that they are friction mounted via a large nut...can't really tell from the inside because they are heavily bedded with something hard.

Any thoughts would be greatly appreciated. I have no idea of their age but the Islander is a'68.

Thanks!

Tom

Figment · Post by **Figment** » Sun Oct 16, 2005 6:30 pm

The common way (that I know) to test bronze thru-hulls is to give two or three good whacks with a big hammer. Either the bronze is corroded and brittle enough to crack, or it isn't.

On the inside, you say the seacocks are nearly new. So you can see the seacocks, but cant see if they have bolts sticking up through them?

Tommy Bahama · Post by **Tommy Bahama** » Sun Oct 16, 2005 9:24 pm

A whack with a hammer sounds like a good enough test to me! I just opened the head locker to make sure that I was relaying the right information. From the inside, the through hulls look pretty new. The installation looks like this;

Through the hull, a 1/4" layer of bedding putty, a 3/8 plywood disk that is drilled to fit over the threaded through hull shaft and a large nut to tighten the assymbely to the hull. I can't see any evidence of bolts or screws that go through the hull into the flange. Is this okay? I would think that the nut would provide a firm enough fit...it's just that every through hull I've seen in catalogs have some sort of mounting screws.

Thanks,

Tom

Figment · Post by **Figment** » Sun Oct 16, 2005 9:54 pm

Tommy Bahama wrote: Through the hull, a 1/4" layer of bedding putty, a 3/8 plywood disk that is drilled to fit over the threaded through hull shaft and a large nut to tighten the assymbely to the hull. I can't see any evidence of bolts or screws that go through the hull into the flange.

From this I infer that you don't actually have true seacock valves on these thru-hull fittings. A true seacock valve has its own flange with bolt holes like these

The seacock flange acts in place of the large nut on the thruhull fitting.

The bolted installations you've seen in catalogs involve a seacock valve like the above. It's the seacock that gets bolted in place, not the thru-hull fitting.

Tommy Bahama · Post by **Tommy Bahama** » Sun Oct 16, 2005 11:43 pm

Ahhhh, now I'm starting to get it. My "valves" while bronze, are threaded directly onto the through hull fitting. Further inspection reveals that they are ball-type valves. The two in the head, I've closed and I removed the handles since we use a porta-potty. I'm wondering if should also remove the valve and just install a threaded cap. The one for the sink, I think that I would like to keep functional.

My cockpit drain through hull doesn't have a valve, just the drain hose double clamped to the shaft...should I install a valve here? I'd think that if the drain hose somehow failed that I'd have a wet boat.

Thanks again,

Tom