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

Jun 21, 2004
2,810
Beneteau 343 Slidell, LA
[QUOTE="TrapperJohn, post: 1840451, member: 166974"
There may be a recessed hull fitting under the bottom paint. I couldn't tell.
[/QUOTE]

Think that your suspicion is correct; likely a flush mount / recessed thru hull fitting that has layers of paint covering.
 

colemj

.
Jul 13, 2004
517
Dolphin Catamaran Dolphin 460 Mystic, CT
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.
How do you know you have 2 pencil sized holes if you haven't seen them yet? If they are near the bow, they could be chain locker drains. You wouldn't want to fill them in.

Mark
 
Jan 11, 2014
12,788
Sabre 362 113 Fair Haven, NY
How do you know you have 2 pencil sized holes if you haven't seen them yet? If they are near the bow, they could be chain locker drains. You wouldn't want to fill them in.

Mark
He obviously knows there are holes and he has identified 2 other holes that he has seen but not been able to get to the other side. I think is probably what the OP meant. He sees holes, doesn't know what they are for.
 

dLj

.
Mar 23, 2017
4,301
Belliure 41 Back in the Chesapeake
Hahaha - well at least it's slower...

dj
 
Jun 21, 2004
2,810
Beneteau 343 Slidell, LA
Trapper,
I know that you are familiar with @Maine Sail’s website. One of the articles discusses use of Groco’s adaptor plate for constructing sea worthy thru hull fitting assemblies. Definitely worth investigating, if you have sufficient space to accommodate.
 
Nov 6, 2017
78
Catalina 30 5611 Stratford, Ct
If it was me, I would try to remove the ball valve first. In order to do that I would use a Forsner bit on a drill and drill up close to where the valve is. Once the valve is gone, I would drill away at the mound of goo down to where the boat fiberglass starts but not into it. Once that is accomplished, I would grind away the rest of the junk down to the original fiberglass of the hull. Then remove the rest of the fitting that goes to the outside of the boat. I would then lay fiberglass over the hole and extend it out 2 inches all around the hole. I would then install a Marlon valve that is not only threaded onto the through haul fitting, but is also screwed into the fiberglass that you just laid around the hole. Using the drill bit to remove most of the junk that’s around the valve will save you a lot of dust and minimize grinding inside of the boat. Good luck with your repair.
 
Sep 27, 2008
153
Hunter 33 salem
Is that a thing? Embedding the fitting? I ask because if its not a thing that Hunter did, then its someones
not so hot repair. Maybe it was leaking and someone piled up a bunch of filler ?

I would put a thru-hull (fitting on both sides of the hull) and call it done forever.

The minimal amount of drag it may pose would more than be outweighed by the durability and dependability.

Just a thought...
 
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Sep 17, 2012
108
Morgan 383 Fairhaven, NY
Morgan was a production boat, back in time when folks were buying "a lot" of sailboats. We all know " the wind is free, everything else should be" jokes about sailors, so Morgan did everything to keep their price competitive.
This is how they did it. No thru bolting. No backing plates. Just glob some resin glass mix around the thru-hull so you can't twist the thru hull out of 3/8" inch thick hull lay up when you put a 2' pipe on the handle. Damn, it worked. They're 45-50 years old!
 
Apr 22, 2025
10
Morgan 321 Oswego
Mysteries solved!

Today I was determined to find some answers. I had to crawl on my stomach to get to the head thru-hulls and did a little measuring to find where the strainer thru-hull should be inside. I think I mentioned in another thread that they set my cradle on 4 courses of cinderblocks so the bottom of the hull is 8 ft in the air and the gunwales are 16 ft to the ground so played acrobat while I was at it. The cradle blocks me from putting a step ladder close to anything on the hull and still reach it.

I climbed up on the cradle and hung from the pad adjustment handles to reach one of the pencil-sized penetrations. They are actually 3/4" thru-hulls that were filled in with bottom paint and gunk. I scraped around to see what was was up and got them all cleaned out. While I was there, I checked the balls. They're still in pretty good shape except for little spots of corrosion or dirt. Couldn't tell very well because I also found out the hull, at least below the water line, is 1-1/2 inches thick minimum. No wonder the boat is so heavy for 32 ft. They weren't kidding that boats of this vintage were heavily built. Oh, and there are no mushroom nor inset heads. You can see the layup around the hole. I'm guessing they screwed a flange into the hull, connected a valve and called it a day, That may explain the pile of resin/fiberglass around each valve.

I found the two head seacocks under the V-berth underneath the black water tank. Similar construction as the pictured one earlier except the mound of whatever is not as big as under the sinks. The valves still turn freely. The supply is still connected but the discharge hose is gone and the valve talipiece is plugged. You can't see it in the picture.
Head Seacocks.jpg


Then I went searching for the mysterious strainer thru-hull. I managed to wrestle the boom out of the way and moved the sailbags to get to the settee. Under the cushion I found a small removeable panel. It was then it dawned on me that there once was an A/C unit in the hanging locker just forward of the settee. There are just wires hanging there now. I looked inside and under a bunch of filters and cut up hoses I found the missing seacock. The install doesn't match all the others and there is a plywood backing plate so I suppose all the others were the OEM installation and this was the add-on. This valve turns freely also and the valve is plugged. You can see the pump just below it in the picture.
AC Seacock.jpg


Since I'm not going to install another A/C unit, I'm now wondering how I'm going to lay up 1-1/2 inches of cloth and epoxy. I think this is going to be the biggest job. I'd appreciate some suggestions such as which cloth(s) I should use and any particular order if using different cloths?

Thanks to everyone who had ideas, suggestions, etc. I'll add to this with pictures as it goes along in case anyone else ever runs into this. Now I've got to get spending those boat bucks.
 
Jun 21, 2004
2,810
Beneteau 343 Slidell, LA
With all the other work that needs to be done, I wouldn’t be concerned about closing up the Air conditioner thru hulls now. Who knows, later on you may decide that a reverse cycle air conditioner / heater would be nice to take the chill off the cabin in spring & fall and to dehumidify in summer. You‘ve got the plumbing, wiring, & ducts already; all you need is a drop in self contained unit. Might run across a good deal in future!
 
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colemj

.
Jul 13, 2004
517
Dolphin Catamaran Dolphin 460 Mystic, CT
I found the two head seacocks under the V-berth underneath the black water tank. Similar construction as the pictured one earlier except the mound of whatever is not as big as under the sinks. The valves still turn freely.
So far, those strangely installed thruhulls/valves seem to be in very good shape, are operable, and I can't find a real argument for why they are actually dangerous even if they don't adhere to a current standard. Personally, I'd probably leave them alone and go sailing.

Since I'm not going to install another A/C unit, I'm now wondering how I'm going to lay up 1-1/2 inches of cloth and epoxy. I think this is going to be the biggest job. I'd appreciate some suggestions such as which cloth(s) I should use and any particular order if using different cloths?
You don't. You treat it like a cored hull, fill with thickened resin or glue in a plug of something (scrap fiberglass, hardwood) to take up the thickness, and reglass the inner and outer 1/4" of skin.
 
Jan 7, 2011
5,485
Oday 322 East Chicago, IN
Morgan was a production boat, back in time when folks were buying "a lot" of sailboats. We all know " the wind is free, everything else should be" jokes about sailors, so Morgan did everything to keep their price competitive.
This is how they did it. No thru bolting. No backing plates. Just glob some resin glass mix around the thru-hull so you can't twist the thru hull out of 3/8" inch thick hull lay up when you put a 2' pipe on the handle. Damn, it worked. They're 45-50 years old!
Seems odd to me that 2 of the valves are buried in epoxy, and 3 others are more typically mounted with backing plates (and sans the blob of epoxy). Hard to believe a builder would do that.

Greg
 

colemj

.
Jul 13, 2004
517
Dolphin Catamaran Dolphin 460 Mystic, CT
Seems odd to me that 2 of the valves are buried in epoxy, and 3 others are more typically mounted with backing plates (and sans the blob of epoxy). Hard to believe a builder would do that.

Greg
Did I miss something? I saw that all of the valves except one were mounted in a teepee of...well, something. The one that wasn't was added by a PO when they added A/C.

Mark
 
Sep 27, 2008
153
Hunter 33 salem
Yes, I concur. The build up thru hulls are more than likely the builder. Lame as it seems.

I also concur with "IF IT AIN'T BROKEN......."

If they are water tight, and they are actuating.....

Move on to something else...
 
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Apr 22, 2025
10
Morgan 321 Oswego
Did I miss something? I saw that all of the valves except one were mounted in a teepee of...well, something. The one that wasn't was added by a PO when they added A/C.
This is correct.

azambella, that is a very tempting course of action but I don't know if I really want to live with it. I've watched it time and again in my last job.

Thanks to all who offered comments and suggestions. I think I'll tackle the galley sink first and that should tell me what's underneath that mess. If things look ok, I may just postpone the others until I've had some water over the keel. The oddball for the non-existent A/C unit has been there for only 15 years or so, the backing plate is not wet nor delaminated and the bronze still looks ok. I can pretty much see the whole assembly. The valve is closed and the tailpiece is plugged so it would have to catastrophically fail.

I'll add some pictures when I get to something I can see. Still waiting for parts to arrive.

Thanks again, you've all been so helpful!