Seacock Question

[C420sailor]

I would absolutely not use a gate valve. No way, no how.

[Bill Seal]

It would seem to be a no-brainer to cut off the mushroom headed pipe to the right length, and then run a npt die over the end to make it compatible with a npt female fitting.

[Manateeman]

You don’t need to thru bolt. The Marine how to article shows you what to do. Use the Groco adaptor plate. Let’s you change valves.
If you clean the hull, rough it up and put the backup pad down with Plexus, it’s not going to move. Don’t get the plexus in the bolt holes...tape the bottoms and Tef-Gel the threads.
The two thread Groco thru hulls are for above the waterline. I don’t use them.
You cannot run a die or even do it on a lathe. Not enough metal.
Just don’t use plastic.
The manatee crew

[Pete7]

Originally Posted by Manateeman

Just don’t use plastic. The manatee crew

Sorry, too late one done and another due to be changed week after next.

TruDesign throughout the boat eventually.

Pete

[deblen]

Originally Posted by Bill Seal

It would seem to be a no-brainer to cut off the mushroom headed pipe to the right length, and then run a npt die over the end to make it compatible with a npt female fitting.

Not enough metal to re-thread a thru-hull. / Len


https://www.pbase.com/mainecruising/..._primer&page=2


https://www.cruisersforum.com/forums...ml#post2890243

[deblen]

https://www.youtube.com/watch?v=lx_Zu9sW_Qk

[NYSail]

When you say they bolt, are you saying with a nut on the other side of the hull? Never saw they before personally. The mushroom typically has a nut on it that tightens it to the hull unless it’s going into a proper fitting. When it’s going into the correct fitting it extends deep. Then you put the screws through the seacock to secure it in place, but only into the backing plate. I ha e a friend that likes to go a bit into the hull, but I’m not of that thinking personally. I used 4200 around the mushroom head only with enough to fill voids in the hole and squeeze out from around the head. I never get it on the threads (Teflon tape or pipe dope or both). I also 4200 the backing plate into place. Maine sail has great article and also groco will talk your ear off how to do it as well.

Good luck
Greg

[C420sailor]

Groco also sells backing plates with integral nuts that you can bond to the hull...eliminates drilling into the actual hull. Send bronze bolts through the seacock or adapter plate into the backer.

[AKA-None]

Originally Posted by C420sailor

Groco also sells backing plates with integral nuts that you can bond to the hull...eliminates drilling into the actual hull. Send bronze bolts through the seacock or adapter plate into the backer.

Like this

[C420sailor]

Yep, nice cock.

[jpendoley]

Originally Posted by Cheechako

I have not used bolts but once. I dislike make a hole in a hull and then adding 3 or four surrounding it. I always used good seacocks and 5200.
Bolts are not bad though probably. I disfigured a finger trying to drill holes in a bronze seacock, so be careful, it grabs drill bits very nicely! then spirals through with the seacock climbing up the drill bit.

So you are concerned that 40 years without bolts is not long enough?
Flanged seacocks without bolts is far far better than a mushroom with a ball valve attached. Think about it... a reluctant valve puts all the force on the threads at the base and there is no support like a flange. That mushroom's threads leave a maximum of 1/16" of material at the thread root with a sharp crevice which may be crack prone..... A good gate valve may be better as there is no leverage to worry about...

Cheechako-this is an excellent observation. It surprises me that an issue so critical to safety is so differerntly construed by very capable people. I think there are two schools of thought on through bolting-one is a belt and suspenders approach and the other is to not overcomplicate an already secure arrangement ie flanged thruhull with mushroom is sufficient. There is uniform consensus that backing plates are mandatory in all applications.
You are right that mine have held up for forty years, but I have no idea how hard it has been sailed before I acquired it. I'm a belt and suspenders guy on the water.
Jim