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Thru hull and seacock installation

3697 Views 11 Replies 7 Participants Last post by hopcar, Feb 23, 2015

luhtag

Discussion Starter · Feb 20, 2015

I recently contracted someone to do various work on my boat and among these things was the removal of and installation of all new thru hulls and seacocks, of which there are 9 total. I had two of them permanently closed up but the others were put in with just the threaded thru hull and backing nut.

This contractor, even with 20 years of experience, was dumbfounded at the suggestion that he use flanged seacocks with backing plates instead of simply screwing a valve onto a thru hull with only the backing nut. He is a motor yacht type, not an offshore sailor. The thru hulls were installed professionally, he used 5200, and they are strong, clean, and look good but they are still only held in with the backing nut that's included with the thru hull. He also prepped, dried, and epoxied the existing holes in the hull so that they are strong as well.

Here is my question: Since this person no longer works for me, and I am going to add backing plates and flanges to all of these thru hulls, do I need to completely remove them all and start from scratch or can I (would you) gingerly screw on and seal a flange adapter to the existing thru hull? They have been in for a number of weeks now and the 5200 is completely cured.

I will remove them and start over if I have to. I'll be finishing this project myself. But I am concerned about breaking loose the thru hull seal as they are when I screw down a flange and seacock. Are the thru hulls strong enough to withstand the torque of adding a flange and valve? Would you have someone outside holding the mushroom head with a spud wrench while making these additions?

Currently I am leaning towards just adding the flanges and valves to the existing new thru hulls. Any advice on this would be hugely appreciated. I really don't want to break all these things out and start over.

We sail extensively and cruise full time with children. Although we don't currently cross oceans we do make hops from the Bahamas to the USVI.

Thanks!

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MarkSF

· #3 · Feb 20, 2015

luhtag said:
I recently contracted someone to do various work on my boat and among these things was the removal of and installation of all new thru hulls and seacocks, of which there are 9 total. I had two of them permanently closed up but the others were put in with just the threaded thru hull and backing nut.

This contractor, even with 20 years of experience, was dumbfounded at the suggestion that he use flanged seacocks with backing plates instead of simply screwing a valve onto a thru hull with only the backing nut. He is a motor yacht type, not an offshore sailor. The thru hulls were installed professionally, he used 5200, and they are strong, clean, and look good but they are still only held in with the backing nut that's included with the thru hull. He also prepped, dried, and epoxied the existing holes in the hull so that they are strong as well.

Here is my question: Since this person no longer works for me, and I am going to add backing plates and flanges to all of these thru hulls, do I need to completely remove them all and start from scratch or can I (would you) gingerly screw on and seal a flange adapter to the existing thru hull? They have been in for a number of weeks now and the 5200 is completely cured.

I will remove them and start over if I have to. I'll be finishing this project myself. But I am concerned about breaking loose the thru hull seal as they are when I screw down a flange and seacock. Are the thru hulls strong enough to withstand the torque of adding a flange and valve? Would you have someone outside holding the mushroom head with a spud wrench while making these additions?

Currently I am leaning towards just adding the flanges and valves to the existing new thru hulls. Any advice on this would be hugely appreciated. I really don't want to break all these things out and start over.

We sail extensively and cruise full time with children. Although we don't currently cross oceans we do make hops from the Bahamas to the USVI.

Thanks!

I am trying to think of a way to save you lots of work. All I can come up with is this :

Make an FR4 backing plate with a hole in it, that will fit over your through-hull. It will need a recess in it for the nut, as that is already stuck on with 5200. Place a second nut over the backing plate, put plenty of 5200 between the plate and the hull, and tighten down. You now have the load spread over a backing plate, without removing the through-hull.

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MarkSF

· #10 · Feb 23, 2015

Yes, but the nut is now stuck in place with 5200.

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