Now that the season is over, it's time to get back and post what I found on my thru-hull expedition. This post is to compile what I found in one spot so the next time someone encounters something similar, they don't have to search all over. Since I posted my original thread, there have been a couple of threads on thru-hulls and maybe it will dispel someone else's hesitation to do the work. If you've already worked on your thru-hulls or done hull work, you may want to pass over this thread as I'm sure you'll be bored.
I have a 1982 Morgan 321. Most of the boat is the original "art work" from the factory including the thru-hulls. If you want to read the originating thread, do so here .
When I first inspected the thru-hulls, I found something like this inside the hull.
The outside looked like this. The only thing I could really see of their condition was what appeared to be dirt/corrosion of the balls when I aimed a flashlight up through the holes.
After the first discussion, I thought I'd chop it out piecemeal since I had no idea what was under that mess. I started with an oscillating multi-tool trying not to destroy the valve but I was only getting small pieces at a time. I then got my 4" angle grinder with a cutting wheel and cut larger chunks away, alternating with the multi-tool because of the clearances. Once I got down far enough, I noticed some bronze showing where there would be a flange & bolt. I hadn't noticed any bolt "depressions" on the outside of the hull so I sanded away the bottom paint and found this.
At this point, I had a better idea what I was working with and put a grinding wheel on the grinder and worked my way down to just about level with the hull. The flange was still visible and the valve was in the way so I cut it off with the cutting wheel as close to the hull as I could get. Then I used the grinding wheel to grind everything away even with the hull. I found that there was still a substantial amount of metal in the flange and the bolts (with the nuts already ground off) stuck to the hull. First I tried cutting the flange in pieces using a cutting wheel and break it out but I chickened out when I had already scored the flange enough times and nothing happened. Next I thought I could pop the bolts out with a drift pin and a quick pop with a hammer. When I did that, the flange broke free and popped out of the hull leaving the bolts still sticking in the hull. I ended up using an EZ-Out (bolt extractor) to break the bolts free from the hull. I'm guessing the threads were epoxied into the hull. I also found that the flange had been embedded in the hull layup about 3/16" leaving a little over 1/4" of hull thickness left and an odd shadow around the hole. It looked & felt like plastic but couldn't get a clear view inside nor outside.
When I held up the old flange to my new Groco flange, the dimensions and bolt pattern were identical so I decided to save the bolt pattern in the hull and just drill the correct size hole for the new thru-hull. I made a pattern with some 3/4" plywood and bolted it in place inside the hull to drill the new hole with my holesaw. (I also used the pattern to drill the G10 I bought for the backing plate.) When I started to drill, this "shadow" popped out of the hull onto the marina pavement. It was indeed a piece of plastic. I'd never seen a thru-hull with a plastic ring about its tailpiece. I was now left with a hole in the hull that was 1/4" wider than the new thru-hull.
Up until this time, the only 4" grinding disks I could find were metal cutting, 36 grit grinding, and concrete cutting -- no flap disks. One day as I was mulling this over, I went into Lowe's for something else and they had a new display of Norton grinding wheels that included 40 grit flap disks. This made it much easier to clean up my mess for the next step. I taper ground around where the old thru-hull was for about 4-5" except the side closest to the wall where I only had 3 inches to play with. I ended up with a dish shaped taper down to the level of the hull where the flange had been. While cleaning this out, I kept running into voids in the laminate so I opened them up as I found them.
I was a little concerned how to proceed. Did some searching online and then I consulted the West System's "Fiberglass Boat Repair & Maintenance" book. In Appendix D, Zone 3 (they categorize the repairs by the risk to hull integrity), they discuss thru-hull replacement when the holes don't match. Since the outer 1/4" of hull was intact and I only need to fill 1/8" around the new hole, I decided to just fill the open hole with epoxy thickened with the West 404 high density filler and paint around the scarf to fill any opened voids. Once that was set up and tacky, I started layering cloth and chopped mat to bring the hull thickness back to original. I wanted to preserve the strength of the hull around that hole by bringing it back to level. Since there was no damage on the outside, it obviated the need to grind and fill from the outside.
To preserve the bolt pattern, I wadded up some plastic to about a pea size and pushed them into the bolt holes from the outside. Once I finished repairing the hull, I could then re-drill the holes from the outside with the old holes as a guide. I ended up using 2 layers of chopped strand mat alternated with the first 2 of 8 layers of 10 oz cloth to bring it fair with the hull. I let that cure for a couple days before I went any further because I was using slow hardener, a newbie to epoxy work, and overly cautious.
At this point, I dug the plastic "peas" out of the bolt holes and re-drilled through the newly patched hull. From there, I could re-install my template and drill the new thru-hull hole to the correct size. Now I was ready to finish the job.
I trimmed and scuffed up my G10 backing plate using the cutting wheel and flap disk. (No big holesaw for the G10 at those prices.) I beveled the edges of the G10 backing plate to minimize hard spots, did a test fit (above), and then epoxied it to the hull using a mixture of the 404 high density filler and the 403 microfiber filler. To keep everything in the correct position, I used some bolts and an XL thru-hull I had accidentally bought when I first started out. It's been a handy guide as I fit things together without messing up the final pieces. All were waxed up to prevent epoxy from sticking.
I installed the flange using Sikaflex 291 on both the bolts and the thru-hull and tightened everything up. Then I let the Sikaflex cure for a day before I screwed on the valve and hose adapter using Permatex thread sealant. I used a similar sealant when I worked at the power plant and it made a great, leak-free fit on systems that ran up to 2000 psi.
And finally ...
I want to thank everyone that commented on the first thread with helpful suggestions. This was my first time replacing a thru-hull and doing epoxy work.
I wrote this long, boring post for those that come after me hesitant to rip apart their boat on their own. When I found these thru-hulls inside the boat, they didn't look like any of the pictures I've seen online over many years of armchair sailing. In the end, it was just a bunch of parts that you'd expect buried in a pile of resin and covered with 14 oz roving.
If you can't find what you need from your chandlery, some of the suppliers I used were:
Defender (defender.com) thru-hulls, sealants, ABA hose clamps
McMaster-Carr (mcmaster.com) bronze hardware, G10 backing plate
Marsh Fasteners (marshfasteners.com) bronze hardware, ABA hose clamps
Coveralls Direct (coverallsdirect.com) Tyvek suits, gloves
U.S. Composites (uscomposites.com) fiberglass cloth, chip brushes, other fiberglass/epoxy tools
Jamestown Distributors (jamestowndistributors.com) West System epoxy kit & fillers
For those who are new to thru-hulls or working with epoxy, here's a few things I learned:
I have a 1982 Morgan 321. Most of the boat is the original "art work" from the factory including the thru-hulls. If you want to read the originating thread, do so here .
When I first inspected the thru-hulls, I found something like this inside the hull.
The outside looked like this. The only thing I could really see of their condition was what appeared to be dirt/corrosion of the balls when I aimed a flashlight up through the holes.
After the first discussion, I thought I'd chop it out piecemeal since I had no idea what was under that mess. I started with an oscillating multi-tool trying not to destroy the valve but I was only getting small pieces at a time. I then got my 4" angle grinder with a cutting wheel and cut larger chunks away, alternating with the multi-tool because of the clearances. Once I got down far enough, I noticed some bronze showing where there would be a flange & bolt. I hadn't noticed any bolt "depressions" on the outside of the hull so I sanded away the bottom paint and found this.
At this point, I had a better idea what I was working with and put a grinding wheel on the grinder and worked my way down to just about level with the hull. The flange was still visible and the valve was in the way so I cut it off with the cutting wheel as close to the hull as I could get. Then I used the grinding wheel to grind everything away even with the hull. I found that there was still a substantial amount of metal in the flange and the bolts (with the nuts already ground off) stuck to the hull. First I tried cutting the flange in pieces using a cutting wheel and break it out but I chickened out when I had already scored the flange enough times and nothing happened. Next I thought I could pop the bolts out with a drift pin and a quick pop with a hammer. When I did that, the flange broke free and popped out of the hull leaving the bolts still sticking in the hull. I ended up using an EZ-Out (bolt extractor) to break the bolts free from the hull. I'm guessing the threads were epoxied into the hull. I also found that the flange had been embedded in the hull layup about 3/16" leaving a little over 1/4" of hull thickness left and an odd shadow around the hole. It looked & felt like plastic but couldn't get a clear view inside nor outside.
When I held up the old flange to my new Groco flange, the dimensions and bolt pattern were identical so I decided to save the bolt pattern in the hull and just drill the correct size hole for the new thru-hull. I made a pattern with some 3/4" plywood and bolted it in place inside the hull to drill the new hole with my holesaw. (I also used the pattern to drill the G10 I bought for the backing plate.) When I started to drill, this "shadow" popped out of the hull onto the marina pavement. It was indeed a piece of plastic. I'd never seen a thru-hull with a plastic ring about its tailpiece. I was now left with a hole in the hull that was 1/4" wider than the new thru-hull.
Up until this time, the only 4" grinding disks I could find were metal cutting, 36 grit grinding, and concrete cutting -- no flap disks. One day as I was mulling this over, I went into Lowe's for something else and they had a new display of Norton grinding wheels that included 40 grit flap disks. This made it much easier to clean up my mess for the next step. I taper ground around where the old thru-hull was for about 4-5" except the side closest to the wall where I only had 3 inches to play with. I ended up with a dish shaped taper down to the level of the hull where the flange had been. While cleaning this out, I kept running into voids in the laminate so I opened them up as I found them.
I was a little concerned how to proceed. Did some searching online and then I consulted the West System's "Fiberglass Boat Repair & Maintenance" book. In Appendix D, Zone 3 (they categorize the repairs by the risk to hull integrity), they discuss thru-hull replacement when the holes don't match. Since the outer 1/4" of hull was intact and I only need to fill 1/8" around the new hole, I decided to just fill the open hole with epoxy thickened with the West 404 high density filler and paint around the scarf to fill any opened voids. Once that was set up and tacky, I started layering cloth and chopped mat to bring the hull thickness back to original. I wanted to preserve the strength of the hull around that hole by bringing it back to level. Since there was no damage on the outside, it obviated the need to grind and fill from the outside.
To preserve the bolt pattern, I wadded up some plastic to about a pea size and pushed them into the bolt holes from the outside. Once I finished repairing the hull, I could then re-drill the holes from the outside with the old holes as a guide. I ended up using 2 layers of chopped strand mat alternated with the first 2 of 8 layers of 10 oz cloth to bring it fair with the hull. I let that cure for a couple days before I went any further because I was using slow hardener, a newbie to epoxy work, and overly cautious.
At this point, I dug the plastic "peas" out of the bolt holes and re-drilled through the newly patched hull. From there, I could re-install my template and drill the new thru-hull hole to the correct size. Now I was ready to finish the job.
I trimmed and scuffed up my G10 backing plate using the cutting wheel and flap disk. (No big holesaw for the G10 at those prices.) I beveled the edges of the G10 backing plate to minimize hard spots, did a test fit (above), and then epoxied it to the hull using a mixture of the 404 high density filler and the 403 microfiber filler. To keep everything in the correct position, I used some bolts and an XL thru-hull I had accidentally bought when I first started out. It's been a handy guide as I fit things together without messing up the final pieces. All were waxed up to prevent epoxy from sticking.
I installed the flange using Sikaflex 291 on both the bolts and the thru-hull and tightened everything up. Then I let the Sikaflex cure for a day before I screwed on the valve and hose adapter using Permatex thread sealant. I used a similar sealant when I worked at the power plant and it made a great, leak-free fit on systems that ran up to 2000 psi.
And finally ...
I want to thank everyone that commented on the first thread with helpful suggestions. This was my first time replacing a thru-hull and doing epoxy work.
I wrote this long, boring post for those that come after me hesitant to rip apart their boat on their own. When I found these thru-hulls inside the boat, they didn't look like any of the pictures I've seen online over many years of armchair sailing. In the end, it was just a bunch of parts that you'd expect buried in a pile of resin and covered with 14 oz roving.
If you can't find what you need from your chandlery, some of the suppliers I used were:
Defender (defender.com) thru-hulls, sealants, ABA hose clamps
McMaster-Carr (mcmaster.com) bronze hardware, G10 backing plate
Marsh Fasteners (marshfasteners.com) bronze hardware, ABA hose clamps
Coveralls Direct (coverallsdirect.com) Tyvek suits, gloves
U.S. Composites (uscomposites.com) fiberglass cloth, chip brushes, other fiberglass/epoxy tools
Jamestown Distributors (jamestowndistributors.com) West System epoxy kit & fillers
For those who are new to thru-hulls or working with epoxy, here's a few things I learned:
- Get lots of protective equipment -- respirator, safety glasses/goggles, coveralls with hood, disposable gloves, lots of rags
- If going to do grinding/sanding -- plastic sheeting and duct tape (lots of it) and seal up everything. Don't be skeptical as I was of the mess thinking you can just vacuum up what you didn't catch. Everything I've opened up this summer had resin dust inside despite my best efforts.
- Despite your best efforts, wet epoxy resin will end up in places you don't expect it. Keep rags and mineral spirits handy.
- If it's even temperate where you're working (over 65 deg F), use the slow hardener. It will give you enough time to work cautiously and still get everything in place before it's cured too much to make fixes.
- Go to Rod's (Mainsail's) website (marinehowto.com) and read his articles on thru-hulls, multiple times if you still have questions.
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