Through-hull fitting replacement
Even in better boatyards, I’ve watched inexperienced workers struggle with skin-fitting replacement. Whether it’s plastic, stainless steel, or proper bronze, once properly installed and generously -usually excessively- buttered with adhesive sealant, skin-fittings can become extremely difficult to remove.
If you’re replacing a faulty seacock, you’ll be lucky to wind it off of the through-hull skin-fitting. It’s not uncommon to find that the effort to do so ends up damaging the threads or breaking the sealant. Usually, the nut is corroded/glued beyond moving. A large enough wrench might move it, but there never seems to be room or access to employ such a tool. Even if you get the nut spun or split off of the threads, the fitting is usually permanently bonded to the hull.
There is a simpler, easier, faster way:
First, pound some softwood dowel or tapered plugs into the fitting from the outside. It doesn’t have to go in too far, just enough to seat firmly and securely.
Cut the wood off flush with the surface of the fitting. It doesn’t need to be particularly neat or clean. Remember, we’re trying to save time and effort here!
Make a center mark on each piece of wood, and break out the hole-saws. Use a quality hole-saw; they’re expensive, but worth every penny. Choose a size that’s just a kerf larger in diameter than the internal diameter of the fitting. Err on the small side; if you’re off, it’ll make less mess, and you can always start over with another piece of wood.
Drill in just about as deep as the hull is thick, or until the outside flange of the fitting pops off, whichever comes first. If the flange doesn’t pop, massage it around the edges with a cold chisel and modest hammering.
Double-check all your new fittings. Make sure you haven’t mixed up any straight-thread fittings with pipe-thread (tapered) fittings. Make sure all the threads are clean. Easier to check this now than once halfway installed!
Install the new fittings. If it’s a cored hull, make sure that it has been properly de-cored in way of the fittings! Use plenty of serious adhesive sealant, such as 3M 5200. You’re looking for even yet not excessive squeeze-out.
There’s a few tools/techniques to hold the fitting in place as you wind on the nut. The best involve a helper outside the boat! Notice that there isn’t any sealant on the inside of the hull; the sealant around the threads and under the outside flange is more than enough to do the job. Excess sealant inside the hull just makes for a mess and more difficulty next time. Seat the nut hand-tight at first, then come back and crank it 1/2 turn harder once the sealant has cured. Lastly, don’t rush to get the sea-cocks wound on until everything is set.
Use good tools, move forward with confidence, and beat the local yardrats at their own game!
