Removing an obstinate thruhull

[Shoalcove]

I've got to remove my current raw water seacock and replace it with a larger one to accomadate my new raw water pump. The trouble is the reluctance of the current seacock to go quietly into the night, as it were.
I have no photos but it appears to be a thruhull with an integrated screen connected to a seacock that has a raw water screen built in. The seacock has four bolts that appear to have their heads glassed over.
I can't twist off the seacock because of the 4 bolts and the thruhull seems very reluctant to move.
I'd appreciate any ideas since my current mindset tends towards a grinder or perhaps switching to a RV!
Thanks,
David

[Case]

Got a Dremel? That's what I used. Cuts very neat and has highly precise control. I used cutting discs with the Dremel for the thru-hull removal.

The fiberglass reinforced discs are best... they are black. The dark brown ones are not as good and tend to shatter but they can work well if you have any on hand.

If you don't have a Dremel... umm... You'll have to wait for others to chime in with alternative methods (and tools).

I have only removed 2 obstinate thru-hulls so far so I am far from experienced in this. The Dremel worked well, though. It cut thru the bronze like a hot knife thru butter.

One caveat... with the Dremel and a cutting disc, be very careful.. you can whiz thru the fiberglass very easily...


- Case

[A30_John]

I'm not sure whether it was proper technique or not, but I recently removed a stubborn through hull using a grinder. The procedure was performed in a matter of minutes with fine results. I echo the previous post about watching where you're going with the grinder. It cuts so fast and so easy you might not realize what you're cutting into before it's too late.

[Tim]

Sometimes, I think it's actually easier to simply cut out a portion of the hull around the obstinate through hull, and then patch the hole. This might seem drastic, but it's really not if you think about it, given the potential in time and frustration savings. Of course, one must be confident with fiberglass repair work to consider this particular course of action.

You can also grind off the exterior flange of the fitting and get it out more easily that way. You can even cut lengthwise through the neck (threaded portion) of the throughull, and then pry the fitting away from the hull as needed. Always be careful not to create collateral damage with any tool, of course. But when they don't just pop out, you often need to resort to significantely more destructive means to release the hold of the sealant.

Careful application of heat can help also.

[Shoalcove]

Thanks for the ideas. I hadn't thought about trying the Dremel so that might be the first attempt. The Dremel would be ideal if it was a normal thruhull and not the more substantial style with a scoop/screen. The grinder will be on site. Perhaps a combo of the two.As far as the fiberglass repairs, I have some 10oz cloth and epoxy to patch any oversights.
This has the feel of one of those little projects that grow and grow. Last year I started rebedding a fitting and ended up replacing most of my SS deck hardware and refinishing the deck and cabin top. Stand by for updates.
Best regards, David

[dasein668]

Sometimes, I think it's actually easier to simply cut out a portion of the hull around the obstinate through hull, and then patch the hole.

If I ever have to remove any of my throughulls/seacocks, which were installed with 5200, this is the route I will go. Directly. Without attempting to remove them in any other way first.

[Figment]

Eh, why bother to remove at all? Just fill the fitting with 5200 and start over elsewhere.

;)

[Quetzalsailor]

I have now done 5 of the 7 throughhull seacocks on Q. None of these went away peacefully. And adding to the issue was my gluing two in as I fitted things.

With the mushroom type, it's pretty easy to grind the mushroom off and, presuming you go slowly enough to not heat the 'glass excessively, there's no danger of damaging the hull. Quetzal has flush throughhulls rather than the mushroom type. My favored way, after failing the attempt to unscrew things using pipe wrenches and cheaters, is to drill the thoughhull from the outside with a multiplicity of 3/16" or so holes around the bore. The idea is to disconnect the flange from the threaded bit. Drill parallel to the bore so that you have less likelihood of slipping off and drilling the hull instead. Drill close together so that you don't have much metal remaining connecting the two parts. Use a nice sharp, small cold chisel and cut the intervening metal. My small chisel is about 3/8" square section. The bronze cuts and drills quite readily. Pop the flange out. Check to be sure you don't have burrs out past the thickness of the bore. Pop the remains off the inside.

It takes 5-10 minutes.

[dasein668]

Eh, why bother to remove at all? Just fill the fitting with 5200 and start over elsewhere.

;)

Oh! Good idea! Why didn't I think of that?

[Shoalcove]

Filling the old thruhull with5200 sounds tempting but, whenever possible, I prefer to things the hard way. Also, I need to put a bigger hole in that spot. It is very difficult to tell how things are connected.
There are no screw heads visible in the screen covering the thruhull but there are 4 areas that look like either where the mold was poured or god forbid, the screw heads were groung off.
I'm thinking that when I get to the boat next weekend, I may start with drilling them out to see if it makes a difference. I'm guessing that I'll end up driving the bolts backwards to see were they exit the hull. I am open to other suggestions.
Thanks for the input.
David

[Ceasar Choppy]

I'd make sure there are actually screws holding it in before you go drilling. Those exterior strainers can come as a one-piece TH, and may not actually be bolted in-- rather just screwed into the seacock.