Plumbing, Head, Part 3, Holding Tank Vent Through-Hull Installation

Installing the stainless steel through-hull for the holding tank vent
Having cut the holes in the sheer stripes for the holding tank vents, I could now install the stainless steel through-hulls. This was a quick little project, but only because I had done a lot of research and a lot of work to get to this point. The steps I took to bring this to completion on Oystercatcher, my Ericson 25, are the subject of this brief posting.
You'll recall from my first posting in this multi-part article that I had routed one of the vent hoses through the hanging locker on the port side of the boat.
At the same time I had installed a valve that would give me the option of closing the vent if the weather got up. This valve was thus a safety measure, an anti-siphoning device.
You'll also recall that I had drilled three different holes - one in the top of the shelf above the hanging locker, one through the alcove box, and a third through the hull.
In the picture below, you can see the hole through the hull quite well.
There was a lot of residue on the hull that likely dated to 1975 when Ericson Yachts manufactured the boat. I used xylene to clean it up. This high strength solvent is good at breaking down adhesives and waxy substances.
It took multiple rubbings with cotton cloths to clean up the sticky area around this hole.
I also needed to clean up the hull on the starboard side of the boat where the head was located.
You'll recall that I also had drilled holes for a second vent hose on this side of the boat.
Just like on the port side, I had drilled a hole through the alcove box. Then I drilled a hole through the hull.
I called upon the xylene once again.
In the picture below, you can see how the xylene has remove the sheen from the surface of the hull and left it with a hazy, satin-finish appearance.
Having completed this thorough cleaning of the hull with xylene, I laid out the stainless steel through-hulls for cleaning.
For these I used acetone, a much milder solvent, yet a good one.
I used it to remove any oil that might have been left on the surface of the stainless steel as a result of the machining process.
For the installation of these through-hulls I used Sikaflex brand polyurethane adhesive/sealant. Specifically, this was Sikaflex 291 LOT. The letters LOT stand for "long open time," which means that you have more time than you normally do to work with this type of Sikaflex. This was the same type of Sikaflex that I used to install the bronze through-hulls that I discussed in my previous posting.
Working with a friend, one of us applied Sikaflex to the flange of the through-hull while the other stood outside the boat and pushed the stainless steel through the hull.
The hole was large enough to allow for some of the Sikaflex to squeeze through it.
Nevertheless, I still applied a little extra on the inside of the hull, so that the nut would form a gasket of sorts, just like the flange would form a gasket of sorts on the exterior of the hull.
In the picture below, you can see what I'm talking about.
My friend held a wrench in the through-hull on the exterior of the boat, while I used the channel lock wrench to tighten the nut.
Then we moved over and did the same thing to the other side.

There was plenty of excess Sikaflex on the exterior of the hull.
Despite its LOT designation, Sikaflex 291 LOT begins to skim over quite quickly. You have to remove any unwanted excess without delay.
Mineral spirits, or its cheap cousin, paint thinner, is good for cleaning up the Sikaflex.
This was a short project, but this was only the case, as I said, because I had completed a lot of work to get to this point.
This ends this posting on how I installed the stainless steel through-hulls for the holding tank vents on Oystercatcher, my Ericson 25.

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