1. I had dreaded the chore of removing the gate valves, which had been installed before the deck mold was craned into place. I’d expected them to be frozen, but after I’d cut off the wheels with an angle grinder and applied my largest pipe wrench to the bodies, they spun off easily enough.
2. The through-hulls appeared to have been installed before the hull interior was gelcoated, and there was no way I was going to get the flange nuts off without the use of brute force. I fetched the trusty Sawzall, and standing outside the hull, made four or five cuts through each through-hull stem. Then my wife knocked the through-hulls out from inside.
3. Because the new Marelon through-hulls were slightly larger in diameter, I enlarged the holes with the trusty Dremel.
4. With the backing plates—made from two pieces of 1/4in fiberglass sheet—epoxied into place, the hull laminate is over 11/4in thick.
5. The hull laminate around the through-hulls was 3/4in thick, and I would have to add a backing plate in order to give the seacock a flat surface to mount against. The previous bronze through-hulls had been in place for a third of a century, and I could not foresee any situation that might require the new Marelon ones to be removed. I therefore decided to glue them in place, using WEST SYSTEM’s new G/Flex epoxy. This is a thixotropic glue that requires no thickening and doesn’t run or drip. It also remains slightly flexible when cured, making it better able to retain adhesion even when bonding materials have different expansion coefficients.
6. After offering up the seacocks, I found that additional spacers were needed. I made them out of some 3/8in UHMWPE I had lying around. This is much superior to plywood or timber for backing plates—it doesn’t absorb moisture and is impervious to most chemicals. On the down side, caulk won’t adhere to it, but it will form a seal.
7. I applied a generous dollop of pipe-thread sealant to each seacock, and then screwed it into place. Forespar recommends that you tighten them only as much as you can by hand. When they were tightened down, all the thread in the seacock body was engaged, except for the last inch.
8. Then we only needed to finesse the new hoses into place, and tighten up the hose clamps. Job done.