Thru-Hull Replacement - How do I get through this mess?

[TrapperJohn]

I've found 2 of the thru-hulls on my Morgan 321 and I know they need replacing. They look like originally installed and don't trust them despite the surveyor saying they were adequate. The ball valves move freely, it's way they are attached that really bothers me. The problem is they are buried in a pile of fiberglass and not sure how I am going to attack them.

Part 1:
My original thought was to use an oscillating tool and to cut away the pile of fiberglass and then see what I have. From the outside, there is no mushroom head so I don't know how it is attached to the hull. I thought I had seen a posting on one of the sailing forums with a similar installation but now I can't find it.

Part 2:
I know I'm going to have to sand away the bottom paint and guessing I'll need to bevel grind around the outside of the hole and re-laminate the hull to provide a good surface to seat the mushroom head. I'll probably need to so something internally also for the backing plate.

Here's a couple pictures:

Q1: I've never used an oscillating tool before. What kind of blade(s) should I be looking for or do you have suggestions for another method?

Q2: Do I need to grind away on the outside of the hull and, if so, what type of fiberglass cloth(s) should I use to rebuild the laminate? Once that's done, should I use some epoxy fairing compound around the repair? I'm planning to strip and bottom paint the hull once I've got these fixed.

I plan on using Groco bronze thru-hulls from MaineSail's recommendations along with some G-10 backing plates. I've read his articles a few times and looked around the web/YouTube for other articles about this but the search results are overwhelming. Any other links would help.

ETA: Does anyone in the Oswego, NY area have a Groco installation tool (THT-530) that I could rent, buy or borrow when the time comes?

 

[Ralph Johnstone]

My original thought was to use an oscillating tool and to cut away the pile of fiberglass and then see what I have.

For me, this would be step #1.

I know I'm going to have to sand away the bottom paint

...................... and this would be step #2.

Then take numerous close ups and post once again and see what the consensus is.

If you have a Porter and Cable Oscillating Tool, I've had the best results in cutting fiberglass using the half circle cutting disk :

Have and extra blade handy as the glass fibers really eat the disk teeth. Make your cut a little high and then slowly grind down to see what's hidden in there.

 

[dlochner]

My original thought was to use an oscillating tool and to cut away the pile of fiberglass and then see what I have. From the outside, there is no mushroom head so I don't know how it is attached to the hull. I thought I had seen a posting on one of the sailing forums with a similar installation but now I can't find it.

For cutting, use carbide blades on the Oscillating tool, any other blade will dull too quickly. I'm puzzled by the mounting. Is that really a pile of resin and cloth around the valve? The valve looks like a standard plumbing brass valve from a HW store. Typically the through hull is secured with a nut and then the valve is screwed to the through hull. Cut away all that crap to see what lies below. Taking a slice out first should give some insight.

I know I'm going to have to sand away the bottom paint and guessing I'll need to bevel grind around the outside of the hole and re-laminate the hull to provide a good surface to seat the mushroom head. I'll probably need to so something internally also for the backing plate.

Maybe not. The flange on the through hull is fairly thin, at best maybe a ¼" at the deepest. The fitting is probably polyester resin which will be pretty brittle by now. Try chipping it away, faster and less mess than grinding.

If the flare is not too deep into the laminate, no need to lay up glass on the outside. Just fill the area with thickened epoxy and sand fair with the hull. Don't use micro balloons, use milled fibers or another high density filler. This works because the the new through hull will provide structure to hull in that section. A short section of waxed PVC pipe can be used to maintain the hole's shape and eliminate the need to redrill the hole. Alternatively, packaging tape wrapped around the pipe will work. Epoxy will not stick to packaging tape.

Q2: Do I need to grind away on the outside of the hull and, if so, what type of fiberglass cloth(s) should I use to rebuild the laminate? Once that's done, should I use some epoxy fairing compound around the repair? I'm planning to strip and bottom paint the hull once I've got these fixed.

You shouldn't need to do this unless you have deeply gouged the laminate. Any fairing should be done with a fairing compound that is rated for underwater use. Interlux Watertite and Total Boat TotalFair are suitable products.

I plan on using Groco bronze thru-hulls from MaineSail's recommendations along with some G-10 backing plates. I've read his articles a few times and looked around the web/YouTube for other articles about this but the search results are overwhelming. Any other links would help.

This will work well. As always there are multiple ways to skin a cat. a piece of G-10 will work well.

 

[Tally Ho]

Looks pretty sketchy to me (and the surveyor said ‘no issue’?)…. Are they all like this?

Almost like the valve was stuck in the hole in the hull and then that glob of stuff put on to hold it (as it doesn’t appear to have a skin fitting). Is there a thick layer of ablative paint covering the head of the skin fitting?

I would start removing the blob of stuff, being careful not to cut into the hull glass and see what comes next. If I am right, after removing the blob sufficiently, you would be able to pull the valve out of the hull.

This is a research project at this point. Just try not to do any harm in the investigation!

Greg

 

[dLj]

That is the funkiest looking thru-hull installation I've ever seen... I'm with Greg on this one, the surveyor said this was OK?????

Your line of attack sounds good - Put in some good seacocks. Get rid of the mess....

dj

 

[BigEasy]

I wouldn't trust much of the surveyor's opinion if he said that thru-hull assembly was OK.
As @dlochner suggested, try chipping away with a chisel & evaluate effectiveness. An oscillating tool might also help. I usually use a course grit (36) disc on an angle grinder to grind off the mushroom head on the outside of hull and push the entire assembly out of the inside of boat; however, I have never changed out a flush mount fitting. Perhaps use the grinder & angle sufficiently at the thru hole & exterior surface interface of the fitting so that the horizontal flange portion breaks away from the vertical tube portion of the fitting to separate the pieces. Then push the assembly into the interior of the hull (after getting rid of all the epoxy fillet on interior). If possible, I would use a mushroom head in future to facilitate easier replacement. Of course, replace the hoses, because those are not compliant for marine use on thru hull fittings.

 

[colemj]

If I squint just right, I can see the skin fitting on the outside. I think it is a recessed thruhull with some fairing over it. That's assuming the tube part is bronze (it looks white, but that could be scale).

The inside part is interesting, but I don't think it is as alarming as others do. It is at least an attempt to give some bearing surface and support to what would otherwise be a weak mounting. I'd just hit it with a grinder with 16grit disc and see what's inside that teepee. I suspect it is bog covered with a layer of glass. Start around the glassed edges and you might be able to just whack it off.

Then grind the head off the skin fitting and pull it through from the inside. You aren't going to be saving any of that, so wanton destruction taking it apart is fine.

Mark

Edit: Oops, I didn't see @BigEasy's post and see they said the same first.

 

[TrapperJohn]

Thank you all for the suggestions and opinions.

First, the surveyor's opinion that they were "adequate" I don't necessarily disagree with. He didn't say they were "good" as he did elsewhere in the report. The valves turn smoothly and there's no wiggling. What especially concerned me is the part that the hose is clamped to appears to be galvanized piping. Regardless, this is 43 year old boat and the PO told me he's never used the head and mainly did weekend sailing when he had the time over the last 9 years. I'd rather be safe than sorry.

I've got the head sink the same way as this one in the galley. The black water overboard and another with a strainer cover I haven't been able to get to yet but I assume they will be similar. I've also got 2 penetrations about the size of a pencil that I also haven't seen yet and have no clue what they could go to. Any thoughts? Hopefully I can eliminate those two small holes and fill them in.

I've now got a plan which was similar to what I was originally thinking. And yes, that does seem to be a pile of epoxy and ?? with roving over the top. It doesn't show up so well in the picture. Thanks again!

 

[Tally Ho]

Can’t wait to see what you find under there!

 

[Peggie Hall HeadMistress]

Please bring me up to speed....are we talking about a head sink drain thru-hull, a toilet intake thru-hull or something else entirely?

--Peggie

 

[Project_Mayhem]

If that's solid glass then you'll want to use a grinder. Oscillating tool will take a LOT of patience but is especially useful for precision work closer to the hull. Get a full face mask. The doube seal will substantially reduce the amount of fiberglass dust you'lll end up inhaling and getting into your eyes. Grinding away in enclosed spaces is not fun. Proper PPE makes it much more tolerable. Don't skimp on masking off the area with tape and plastic sheeting. The dust will get everywhere. It will be impossible to get it all out of tight spaces

 

[BigEasy]

Can’t be critical of an installation that lasted 43 years! Installer no doubt glassed around thru hull & valve to provide rigidity & strength to the assembly. Two problems is that you can’t see the condition of the metal under that mass of glass; if de-zincification was occurring on threads of thru hull fitting, you wouldn’t be aware of it. AND, you wouldn’t want to be the guy to deal with it when it’s time for replacement. Good luck with this; keep us apprised of your progress.

 

[BAD ORCA]

Looks pretty sketchy to me (and the surveyor said ‘no issue’?)…. Are they all like this?

Almost like the valve was stuck in the hole in the hull and then that glob of stuff put on to hold it (as it doesn’t appear to have a skin fitting). Is there a thick layer of ablative paint covering the head of the skin fitting?

Thats my guess. I had a skin fitting for an old foot pump intake mysteriously show up when i had my bottom painted.

 

[BAD ORCA]

If that's solid glass then you'll want to use a grinder. Oscillating tool will take a LOT of patience but is especially useful for precision work closer to the hull. Get a full face mask. The doube seal will substantially reduce the amount of fiberglass dust you'lll end up inhaling and getting into your eyes. Grinding away in enclosed spaces is not fun. Proper PPE makes it much more tolerable. Don't skimp on masking off the area with tape and plastic sheeting. The dust will get everywhere. It will be impossible to get it all out of tight spaces

agreed. I used 40 grit flap wheel on an angle grinder to do mine. Made short work of it. The cleanup took longer than the grinding.

 

[Ralph Johnstone]

Whatever you do, I again urge caution as opposed to other comments. If you damage the existing hole the thru-hull occupies, you will find yourself forced into:

a) rebuilding the area to drill a new hole or
b) find yourself forced into going up to the next size of thru- hull.

Either way, don't make a lot of extra work for yourself.

 

[Project_Mayhem]

agreed. I used 40 grit flap wheel on an angle grinder to do mine. Made short work of it. The cleanup took longer than the grinding.

I'd use a cutting wheel for most of this and a flap closer to the hull. I never did manage to get all of the fiberglass dust out of that boat

 

[TrapperJohn]

Peggie,

Pictured and the one I am going to tackle first is the galley sink. The sink in the head is similar but couldn't get a clear a picture. I can't get to it as easily because the boom and sail bags are in the way but I'll still be twisted up like a pretzel to work on it. As for the others I mentioned, I don't know where they go exactly because I can't get to them yet. I'm suspecting some cabinetry will have to be worked on when I get that far.

There may be a recessed hull fitting under the bottom paint. I couldn't tell. The picture may be misleading with artifacts from when I resized the picture before posting. Yes, there is a thick coating on bottom paint over it. That's all got to come off before I repaint.

Tyvek suits are on my shopping list.

 

[FastOlson]

A local yard guy once pointed out that while sanding and chipping away might be interesting if one's time is not valued highly, they would almost always only ascertain the width of the metal outside flange. Then drill the whole unit out in a few minutes with a a hole saw. Grind back and reglass the opening as needed for strength and include a G10 backing place set in epoxy. Then drill and install a modern (and safe) thruhull sea cock. Marelon or bronze... whatever the owner agrees with. Do it right once, and once is enough. Replace the ancient hose, also.
(While boatyards do get dinged for "inflating" their labor bills sometimes, most of them really do Not like redoing their own work. Both the yard & the boat owner benefit from work done right the first time...)

Trivia: a Morgan 321 moors on the next walk over from me and the owner seems to like it a lot and uses it often. It's a pretty big boat (11K) for its stated length.)

 

[dlochner]

The black water overboard and another with a strainer cover I haven't been able to get to yet but I assume they will be similar.

The strainer covered through hull is the intake for the sea water engine cooling.

The black water discharge can be removed and then glassed over as overboard discharge is not permittied in the Great Lakes. This is a bigger project because the hull has to ground back to a 12:1 bevel and multiple layers of glass applied, faired, and painted.

I've also got 2 penetrations about the size of a pencil that I also haven't seen yet and have no clue what they could go to. Any thoughts? Hopefully I can eliminate those two small holes and fill them in.

Where are they located? Some boats have cockpit drains that exit beneath the waterline.

 

[smokey73]

I have a hard time imagining a cockpit drain the size of a pencil? Wouldn't take much debris to clog that and flood the cockpit For that matter, I can't imagine any water intake or overboard that is only the size of a pencil.