Installing Thru hulls

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Oct 6, 2007
Vessel Name
Vessel Make
1983 42' Present Sundeck
I posted this beneath another thread and got no bites. Can anyone help? I could install a valve at each one to get the threads to work but would like to avoid the expense. One TH will be a new vent tube to my blackwater tank and the other is for an additional bilge pump.

I*have to install two thru hulls well above the waterline. *I just got in my TH's (NPS),*and my 90 degree barbs (NPT)-*all bronze. It looks like I need a union of some sort to connect the TH to the 90 degree barb. I looked at Groco (and emailed) and Jamestown without finding anything. Any ideas?
Even if the through hull is above the water line a shut off valve should still be installed, then you should be able to screw in the 90 elbow into the valve.
Phil I don't agree with you about installing shut offs to thru hulls above the water line. But I would like to understand your reasoning. To add a shut off valve to every thru hull would add another 3-6 inches sticking out from the inside of the hull, creating an obstruction if you can even get them in some places.
In my case I have 6 fuel tanks with vent lines, 2 waste tanks with vents, 2 water tanks with vents, 4 bilge pumps, 3 A/C thru hulls, 2 generator exhaust thru hulls, 2 main engine water bypass thru hulls and a cockpit drain, that are all at or above the water line. Most of these are 3 or 4 foot above the water line, what would a shutoff do for me?
Steve is installing a waste tank vent that should be very high on the hull and a bilge pump thru hull that I can't imagine shutting off.
You nailed it. I will return the 90 degree barbs and order these. Thanks everyone for your help.
Thru hull shut offs above the waterline is and should be totally optional. There are arguments to be made on both sides, while we're at it lets include the exhaust thru hull shut off as well. For all those who believe you can never be safe enough, do you have proper evacuation pumps 10-15,000 gph or worthless bilge pumps?
Thru hulls with valves are a great idea for anything that goes under the HEALED waterline.

4 ft up on a motorboat would not be a hassle without other really big problems.
It is not uncommon to have valves on through hulls above waterline. My Defever has them for washer, bilge pumps and sinks. I've not checked the ACs as the likely valve position is hidden from view. Over kill*? On a vessel used for blue water or offshore work I don't think so. Air intakes as high up as possible or better yet inboard are a good thing too.
As much bashing as the Marine Trader line gets from some I'd like to report that all of our original thru hulls above or below the waterline including deck drains and even sinks have shut off valves. I guess they didn't pinch every penny after all.
Jim, Steve mentioned he needed a coupling*which a valve can be.* Not knowing how far above the water line the bilge and vent are seems to be a good precaution.* Many bilge/vent though hulls are close to the water line and if the boat keels or sinks very far then they may be below the water line.* All the thru hulls on the Eagle below and above the water line have valves, and double bilge pumps which exit on opposite sides.* Anyway, I believe all though hulls should have a valve and all exhaust should have a back flow flapper thingy.
Thanks for all the good advice. I think that for my application no valve will suffice. The through hulls will be a good bit above the water. Enough so that if I list that far- long enough to worry about water intrusion- I will have much bigger worries to be concerned with. Thanks all!
Just DON'T follow the advice in PM.

They show a thru hull being perminantly glued in place with 5200.

Big NO NO on an inspected vessel where thru hulls will be pulled for inspection.

The Seacock bolted in place keeps the water out of the boat , the thru hull just seals the penitration in the hull.

Phil, and every one else, Thanks for you thoughts! Have a great day!
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