Plumbing, Head, Part 2, Through-Hull Replacement

One of the new bronze through-hulls, dry-fitted into place
Having cut and dry-fitted the new hoses for the new head and holding tank, I could now focus more closely on the bronze through-hulls that I had earlier purchased for this project. My replacement of the original bronze through-hulls was such a time-consuming task, that I ended up writing about this work separately in a series of ten postings on this blog. In this posting, I summarize this work for the sake of situating it in the context of the broader project that I carried out in the replumbing of Oystercatcher, my Ericson 25.
The toilet on this boat at the time of purchase in 2009 was a Raritan PH I. Now, at almost 40 years of age, it had reached the end of its life. It wasn't worth trying to service it with expensive parts.
The Raritan PH II had long since replaced it. I knew I had to get rid of this old one.
The water intake seacock was in bad condition, just like the rotten backing plate on which it was mounted.
The waste discharge seacock was even worse.
This led me to wonder about the condition of the original bronze through-hulls.
I pulled them with this homemade device.
It looked to me like they had been in place from the very start.
I cleaned them up and inspected them closely and found pits in the bronze. For this reason and others, I decided to replace them.
I researched Marelon through-hulls, flanges, and seacocks, but I didn't like the idea of having plastic hardware. I also had heard of Marelon seacock handles breaking. I therefore opted for Groco brand bronze hardware.
Above we see the flange and seacock for the waste discharge through-hull (not pictured). Below we see the flange and seacock for the seawater intake through-hull (also not pictured). In both of these pictures, I am attempting to figure out how to construct backing plates for the flanges.
The original through-hulls were flush-mounted, not mushroom headed. The new through-hulls that I purchased were also flush-mounted. The only problem was that their flush-mounted heads were smaller than the originals. Therefore, I had to resize the holes with epoxy and then chamfer them with a Dremel. This took a lot of time.
I also had to widen the original hole for the seawater intake through-hull. I did this by hammering a plug into the hole and then using the plug as a centering device for the hole I cut with the hole saw. At the same time, I used a large hole saw to cut a larger hole through the hull liner for the backing plate that I would soon install here.
Then I surrounded both of the holes with duct tape. This would protect the hull liner from any epoxy that I might spill in my gluing up of the backing plates.
The mahogany backing plates were doughnut shaped. Necessity dictated that they be shaped in this fashion, because there were bulges in the fiberglass hull from the hull lay-up manufacturing process - when indentations were made for the original flush-mounted through-hulls. The inside of these mahogany backing plates received many layers of cloth and epoxy. The exterior of the mahogany received cloth and epoxy as well.
Later, after the epoxy had cured, I came back and sanded the surface to a smooth finish.

I then used a hole saw to cut holes through the backing plates.
I had to use a right-angle attachment to cut the hole for the water intake backing plate. The bunk of the trailer obstructed me from drilling it the normal way.
Now I could install the bronze flanges.
This, of course, required me to drill three holes for each flange through the hull.
Outside the boat, I needed to chamfer the holes so that the heads of the bronze screws would sit beneath the surface of the hull.
Now my work on this part of the project was almost finished. Later I would come back and permanently (or a least semi-permanently) install the flanges and the through-hulls with Sikaflex adhesive/sealant.
This ends this summary of the steps I took in my installation of new through-hulls for Oystercatcher, my Ericson 25.

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