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Old 11-08-2011, 23:07   #1
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Thru Hull Threads

I'm about to change my Sea Cocks on all my thru Hulls and they have green corrosion on them. I want to know should I put any teflon tape or pipe goop on the threads of the thru hulls before I screw on the new sea cocks?
Also what works to clean all the corrosion off the thru hulls. I was thinking a soapy solution with a stiff brush.
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Old 12-08-2011, 00:23   #2
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Re: Thru Hull Threads

If your screwing the valve onto the thruhull, it's not a true seacock. Seacocks are mounted to the hull and the thru hull is screwed into the valve from the outside.

If yours is below the waterline then an upgrade is in order. Maine Sail has a good link (and others) to a proper set up: Seacock & Thru-Hull Primer/Pre Information Photo Gallery by Compass Marine at pbase.com

Also see the CF link on threads: Wood Backing Plate for Thru-Hull Soft and Rotten

BTW clean off the green stuff with a SS wire brush. If it has any pink underneath then it's time for replacement.
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Old 12-08-2011, 06:41   #3
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Re: Thru Hull Threads

Quote:
Originally Posted by delmarrey View Post
If your screwing the valve onto the thruhull, it's not a true seacock. Seacocks are mounted to the hull and the thru hull is screwed into the valve from the outside.
Something weird here.
So I have a ball cock thats fixed half open.
When I haul in a few weeks, are you saying I will have to remove the whole thruhull fitting to get the ball cock off? And then put in a new thruhull fitting and new ball cock?

And a special tool is needed for that that won't be available in the boat yard in the back blocks of Venuzalea?

Why not just unscrew the existing ball cock and replace with a new one?

Mark
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Old 12-08-2011, 07:05   #4
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Re: Thru Hull Threads

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Originally Posted by MarkJ View Post
Something weird here.
So I have a ball cock that fixed half open.
When I haul in a few weeks, are you saying I will have to remove the whole thruhull fitting to get the ball cock off? And then put in a new thruhull fitting and new ball cock?

And a special tool is needed for that that won't be available in the boat yard in the back blocks of Venuzalea?


Mark
Yes! If it's a true seacock.

And that special tool? Mine is one size fits all.

If it's a screw-on valve, and the thruhull fitting is eroded, the valve may just brake off.

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Old 12-08-2011, 07:22   #5
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Re: Thru Hull Threads

How many years for a propper marine fitting to become suspect?

as in stanbding rigging 10 years.... etc?



Mark
PS I hate it when a simple job starts evolving.... LOL
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Old 12-08-2011, 07:36   #6
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Mark, how big is the ball cock in question, and is there a set screw type fitting on the side? I replaced mine a couple of years ago and the new ones have a screw on the side I can remove and spray in some sort of lubricant -- used wd40 on one of them once to free it up after it had frozen in the yard.

As for age, I'd check for pink yearly and replace as needed.

hth...
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Old 12-08-2011, 07:43   #7
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Re: Thru Hull Threads

AFAIK Bene's have thru-hull fittings fastened with a nut and then a regular ball valve stuck on top of that...

My 2 cents: find a wrench/spanner that fits into the thru-hull fitting from the outside and can block it from turning, engaging the ribs inside the fitting. Fasten a cruisers-vice (vice-grip) to it and position someone who knows clockwise/counter-clockwise directions () right there at the spot.

On inside, find some hardware to turn the valve. Now the person outside needs to put some force on the fitting counter-clockwise while you do the same on valve. Really, the fitting should be prevented from turning... if it does anyway, it needs to come off.

The threads under the valve will show true color: pink means fitting must be replaced.

I would not bother with all this... just order new fitting and new valve (or if you want to improve design and have enough room, buy the stuff MaineSail shows on his site) and put in new. Only when you have fancy flush head fittings instead of mushroom head, you must make sure the new one will fit etc.

ciao!
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Old 12-08-2011, 07:53   #8
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Re: Thru Hull Threads

Thanks guys. Its next weeks research problem.
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Old 12-08-2011, 09:36   #9
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Re: Thru Hull Threads

sv/ Jedi brings up a critical step and that is not allowing the through hull to rotate while you try to remove the "ball valve" on the inside.
- - This can be done by finding a socket wrench socket that just slips inside the through hull from the outside. There are normally two ridges inside the through hull fitting and you can use an angle grinder to make slot in the socket wrench socket's outer rim that align with the through hull ridges. This "tool" along with a breaker bar can be used to keep the through hull from rotating, and of course also used to install a new through hull if that is found necessary.
- - The suggestion to wire brush the threads of the through hull that are exposed inside the hull is very important. If there is some "pink" showing then the bronze through hull will most likely fail/break during removal of the old ball valve. In any case the through hull needs replacing. Don't forget to keep a wooden cone plug tied to each through hull.

- - The argument about whether ball valves are "sea cocks" is long and old. The theory is that you should be able to stand with your full weight 90 degrees to the axis of the through hull/seacock and not break it. To achieve this there are seacocks with mounting pads (bottom two photos) that are bolted/screwed to the hull or a strong backing block and then the through hull is inserted and screwed into the seacock from outside the hull.
- - These days with making boats to a "price point" it is common to see the old through hull with a backing nut and then a ball valve sitting on top of it (top two photos). Whether you want to get involved in installing the mounting pad type sea cocks or just stay with what you have is - as are most things in cruising - a personal decision usually driven by cost and time involved in replacing the whole set up and your comfort level with the possibility of having a ball valve/through hull break if hit with a significant side load. Don't forget to keep a proper sized wooden cone plug tied to each through hull.
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Old 12-08-2011, 13:09   #10
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Re: Thru Hull Threads

Nicely put Osirissail. Groco makes a nice tool that allows one person to install a thru-hull fitting without an outside helper: Groco Thru-Hull Fitting Installation Tool
A lot of people use it as a wrench for thru-hull removal as well but it isn't really designed for that.
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Old 12-08-2011, 15:16   #11
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Re: Thru Hull Threads

Ahem!

I am planning on adding a fairing block much like mainsails. I was going to use marine grade plywood covered with GRP but now I think I will make ones out of just GRP.
Anyway is there anything I can use Chemically to clean the threads as they are corroded with green and need to be.
Here's the plan
1.0 Fairing block to Glass hull with epoxy
2.0 Groco Flange screwed down to block
3.0 Bolt flange into Fairing block
4.0 Put seacock onto threads
5.0 Attach hoses with 2 stainless clamps

But what can I use to clean the threads after I use a small brass brush on them? Acetone?
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Old 12-08-2011, 16:55   #12
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Re: Thru Hull Threads

I would suggest that the boat should be out of the water when you do this. You should remove the through hull fitting from the boat and then clean and inspect it.
- - Then go ahead and install your backing block. After curing, hole drill out the block from the outside to align the hole in the hull and the block.
- - Temporarily thread the through hull fitting into the new seacock from the outside while positioning the sea cock correctly for easy operation considering surrounding hoses and equipment and bulkheads.
- - Bed and bolt the sea cock to the backing board. Then bed and permanently install the through hull fitting using a tool I described or that HopCar described. Then the only stresses on the actual through hull fitting will be the tightening/compression of the hull.
- - It is important to orientate the sea cock to a convenient and operational orientation. Trying to thread a new seacock onto an existing through hull which is in place will normally result in less than optimal orientation.
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Old 13-08-2011, 16:57   #13
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Re: Thru Hull Threads

Quote:
Originally Posted by osirissail View Post
I would suggest that the boat should be out of the water when you do this. You should remove the through hull fitting from the boat and then clean and inspect it.
- - Then go ahead and install your backing block. After curing, hole drill out the block from the outside to align the hole in the hull and the block.
- - Temporarily thread the through hull fitting into the new seacock from the outside while positioning the sea cock correctly for easy operation considering surrounding hoses and equipment and bulkheads.
- - Bed and bolt the sea cock to the backing board. Then bed and permanently install the through hull fitting using a tool I described or that HopCar described. Then the only stresses on the actual through hull fitting will be the tightening/compression of the hull.
- - It is important to orientate the sea cock to a convenient and operational orientation. Trying to thread a new seacock onto an existing through hull which is in place will normally result in less than optimal orientation.
I will next year but I have a sea cock dripping right now because I accidently knocked the neck and broke it off. It was used for the galley sink drain and has been replaced but they must have used the same old neck fitting.
I'm worried that they used a less then decent sea cock and I am worried about it not sealing and getting worse. It had me scared to death when I was moving the boat to where it is now.
The sea cocks in the Head are completely wore out also so all in all I need to replace 4 sea cocks and get the 2 for the cock pit drains loosened up and lubed. They are original bronze and look to be in good shape just jammed up.
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Old 13-08-2011, 19:44   #14
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Re: Thru Hull Threads

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Originally Posted by w1651 View Post
I will next year but I have a sea cock dripping right now because I accidently knocked the neck and broke it off. It was used for the galley sink drain and has been replaced but they must have used the same old neck fitting.
I'm worried that they used a less then decent sea cock and I am worried about it not sealing and getting worse. It had me scared to death when I was moving the boat to where it is now.
The sea cocks in the Head are completely wore out also so all in all I need to replace 4 sea cocks and get the 2 for the cock pit drains loosened up and lubed. They are original bronze and look to be in good shape just jammed up.
What do you mean by "Neck?" - Do you have a flanged "seacock" or a "ball valve mounted on a through hull stem (threaded interior part)? See above pictures. What broke off? The part attached to the sink drain hose? Or the whole valve from the through hull?
- - Assuming you are in the water and not planing to haul until later in the year then trying to install backing blocks is - IMHO - not a good idea as you would need to remove whatever "valve" you have attached to the through hull and have an open hole right out through the boat.
- - If you broke the seacock/ball valve off the through hull fitting (inside threaded portion), then you must have some sort of plug in the hole.
- - If you broke off the hose nipple/adaptor on the seacock/ball valve that is attached to the sink drain, then all you need to do is to attach a strong tool like a chain-vise grips to the valve body and use a wrench or another vise grip to remove the broken hose adaptor and replace it.
- - In that case simply live with the leaky valve until you are ready to haul and do the job correctly.
- - How do you "wear out" a seacock? If you fail to clean and maintain it, the valve will become difficult or impossible to close/open. But that just means disassembling the seacock/valve and lubing it.
- - In any case make sure you have wooden or other type cone plugs ready to close the hole should the valve break off at the through hull stem (inner threaded part), which is highly probable if you try to mess with removing the valve. At least make sure the boat is in water no more than a foot or less deeper than your keel.
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Old 14-08-2011, 04:44   #15
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Re: Thru Hull Threads

This step-wrench* makes the installation of standard Groco thru-hull fitting possible by a single installer. Slide the thru-hull fitting, flanged end first, over the tool.(It will stop at the proper step). Tie a length of monofilament to the eye and place it into the already cut hole in the hull of the boat. Apply caulking to the falnge of the fitting, and pull the fitting through the hose and against the hull from inside the boat. Thread the monofilament through the locknut or seacock. With the fitting pulled firmly against the hull, the locnut or the seacock. With the fitting pulled firmly against the hull, the locknut or the seacock may be screwed onto the fitting from 1/2" up to 3".

* Grocco #GROCO THT-530
http://www.groco.net/SVC-MAN-07/Sec4/PDF/IBV-FBV-TB.pdf
http://www.groco.net/07-ftgs/tht-530.htm
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