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Discussion Starter · #1 ·
I have an old Groco SV thru-hull & seacock that needs replacing. There is no room above the seacock to unscrew it upwards and off, so the thru-hull HAS to be unscrewed down and out. I torched it to break it free and it did rotate maybe one degree before the dogs inside broke off. I've got PB blaster soaking in it for now.
But I am stumped on how to get this apart. Grinding off the mushroom isn't an option because I'd then need to raise it up from the inside and like I said earlier, I don't have any headroom to do that.
One idea I'm considering is grinding opposing flat spots on the mushroom for a pipe wrench to grab. But the mushroom doesn't stick out very far so this won't be easy.
And there is no room under the floorboards to get a sawz-all or grinder on any part of the seacock. Terrible installation.

Any good ideas on how to unscrew the thru-hull now that the dogs are broken off?
 

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Bronze is soft. Get an electric sawzall or a hack saw. Cut between the valve and the thru hull. Or cut the valve in parts. It wont take long. Just cut it out. Take out the valve and then cut the nut to the thru hull or once the valve is gone stick the saw blade into the thru hull and cut it in two places 180 degrees apart dont cut too deep to the hull and take the two halfs out. Good luck.
 

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I have an old Groco SV thru-hull & seacock that needs replacing. There is no room above the seacock to unscrew it upwards and off, so the thru-hull HAS to be unscrewed down and out. I torched it to break it free and it did rotate maybe one degree before the dogs inside broke off. I've got PB blaster soaking in it for now.
But I am stumped on how to get this apart. Grinding off the mushroom isn't an option because I'd then need to raise it up from the inside and like I said earlier, I don't have any headroom to do that.
One idea I'm considering is grinding opposing flat spots on the mushroom for a pipe wrench to grab. But the mushroom doesn't stick out very far so this won't be easy.
And there is no room under the floorboards to get a sawz-all or grinder on any part of the seacock. Terrible installation.

Any good ideas on how to unscrew the thru-hull now that the dogs are broken off?
Carefully grind the mushroom head off the thru-hull with a 4" angle grinder. Then go inside an simply pull the valve to the right or left and it should tip free. If not cut the valve off the thru-hull inside the boat and the use a pipe wrench on the threads of the thru-hull to twist it out..

PB Blaster won't do much of anything to 5200 you'd be better off to try DeBond.. Now you can understand why many folks are opposed to 5200..:D
 

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Courtney the Dancer
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Xort- would you have enough room to get a small die grinder in there to cut the valve off? You would need an air compressor so shore power would be necessary, not sure of your situation. I'm pretty sure you can rent small pnauematic grinders, maybe even right angle ones if you don't have one. Hard to figure out without seeing it. Good luck.
 

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Another option

Xort,

The above options look quicker and easier, but if they don't work for you here's another.

Carefully grind a couple of slots on either side of the mushroom across the center of the through hull. You'll then (hopefully) have a place for a piece of 1/4" steel plate to gain purchase and act as a really big screwdriver head. Add a pipe wrench (one inside around the seacock) and a big adjustable wrench (on the steel plate) and give it a turn. You may need to add an extension (like a pipe) to the adjustable wrench to get enough leverage to get things moving.
 

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Discussion Starter · #8 ·
There is absolutely no room inside the boat under the floor to get at the seacock. And besides, they ran all kinds of wires around the seacock that I hope to move after it is off. If I start running a sawzall I'll cut some wires for sure; antenna wires and other stuff I do not want to splice.

There aren't any bolts to the flange on this Groco. I think I can see threads of the thru hull looking down into the side of the seacock. I have the big rubber plug out of the seacock. Am I wrong in thinking the seacock is threaded directly into the thru-hull? How long is this threaded area likely to be? From what I can see it looks like maybe an inch of threads into the seacock.
I have zero room to unthread the seacock upward off the thru-hull; I have to unscrew the thru-hull downward out of the hull & seacock.

Cutting a notch in the mushroom is similar to my idea of grinding two flat spots to accomodate either a pipe wrench or a big set of slip joint pliers. I'm afraid I won't get a very deep & neat slice to make a tight fit for the big 'screwdriver'.

I was using PB blaster to free the threads between the seacock & the thru-hull.


What am I missing?
 

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If you take your grinding wheel and place it across the opening of the mushroom hole, with the wheel perpendicular to the hole, you should be able to grind a couple of 1/4" slots as PorFin suggests. Then just get a piece of 1/4" plate and cut/grind it so it will fit in the slots. You'll avoid risk to the fiberglas around the mushroom head that way. You should be able to grind two or three separate sets of slots if you round out the initial ones. There should be a compression ring, that you might not be seeing that holds the mushroom headed thru-hull secure...not the seacock.
 

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I agree with the "cut a slot in the mushroom head" school of thought. Grinding a couple of flats lays you open to doing nasties to the hull.

However, what puzzles me is how the **** did they get the thing in there in the first place? Has something been built around it since it was installed? I have come across some awkward seacocks in my time, but never one that sounds as inaccessible as yours.......

Good luck

Stuart
 

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Discussion Starter · #12 ·
L
I suspect the floor was built over the installed seacock.

Sway
my grinder has a wider grinding wheel. I'll have to search out a thinner grinding wheel. I suspect it won't be hard to find.


Freekin pink seacock!

This is only the beginning...re-attaching the head hose will be even more fun. The top of the seacock is a 90 degree elbow and it points away from the itty bitty access hole in the floor. Reaching the clamps is about impossible. I hope there is some extra in the hose for it to come closer to the access hole to be able to detach it relatively easy after the seacock is detached. Leaving the last part, re-attachment, the most difficult. Don't even suggest pulling up the floor, the seacock sits directly under the door frame to the head and the head floor is a one piece fiberglass unit.

I love boating! I love boating! I love boating! I love boating!
 

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Look for a cut-off wheel in the proper wheel diameter for your grinder. You can always make the slot wider as necessary. I'm betting though that you've got a compression nut on that thru-hull inside where you cannot see it. Once you get the thru-hull turning though, it may become apparent.
 

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Discussion Starter · #14 ·
Compression nut would be under the seacock, on top of the backing plate?

Seacock would be screwed onto the thru-hull down as far as the compression nut?

Thanks all so far.
I'll be picking away at this over the winter. Hope to get it removed before things get real cold then install new as soon as it warms up.
 

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Here's what I think I would do (hard to be fully confident not knowing some stuff).

I assume from your comments above that you can at least get a Stilson wrench or something to the seacok inside to hold that while you turn from under the boat? If yes, that's good for my plan.:p If not, don't bother reading any further.

Then I would drill four holes (say 6 mm) in a round thickish (say 10mm, sorry I can't think in inches :( ) steel plate roughly the same size as the mushroom. Using the plate as a guide, drill the exact same four holes into the mushroom taking care not to penetrate the hull. That's not hard, right?

Then weld some pegs into the holes in the round plate and weld a handle of sorts to the plate as well. If you have followed me so far, this "widget spanner" will not look unlike the tool that comes with an angle grinder to free the disc.

The widget spanner on the outside, a Stilson or other appropriate wrench on the inside and Bob's you auntie.

Good luck.
 

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Compression nut would be under the seacock, on top of the backing plate?

Seacock would be screwed onto the thru-hull down as far as the compression nut?
Could be - a common arrangement involves the installation of the mushroom with a big nut on the inside (and I am not referring to the person holding the stilson here). This leaves a longish threaded portion inside the boat and the seacock is screwed onto this. However, it usually doesn't screw all the way down to the nut.

If you actually cannot get a grip on the nut or the seacock, then it is unlikely (I understate here) that you will be able to use any of the "screw the mushroom off from outside" techniques and will have to fall back on grinding it off from the outside and hoping you can waggle it enough inside to get it out.

"Freekin" describes it well, I think!

Stuart
 

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This may be the most expensive way, but...........

How about filling the center of the thru-hull fitting with a plug or dowel and then drilling out the whole shootin' match with a metal cutting holesaw that is the same size as the outside diameter of the thru-hull fitting. Once you get through the flange you should be good to go, but if need be, you can keep going until you get to the other side of the hull. If there is something above it, slow down as you get through so you don't cut through all of a sudden and damage something on the other side.
 
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