deep, run the bit backward. Chamfering will
prevent the threads of the screw from pulling
the gelcoat up away from the glass, which
can make it impossible to properly seat and
seal your port.
If you had to cut through coring, or if
your holes for the mounting hardware pass
through coring, now’s the time to seal the
edges with epoxy or similar to prevent any
leaks from saturating the core.
Now it’s time to dry-fit your port and, in the
case of some ventilation ports, choose which
way to install the trim ring. If you cut your
opening properly, the port should fit in easily
with about 1/8-inch all the way around to
allow space for the sealant plus expansion to
take place. If it’s tight, you’ll need to file the
edges to make the hole large enough for the
port to fit easily.
Seat anD Seal
After you’re satisfied with the fit and alignment of the predrilled holes (you may need
a helper on the opposite side to assist you
here), snug up the port
temporarily. If everything fits and looks as
it should, you’re ready
for sealant. Most port
manufacturers recommend Dow 795, or
any other 100-percent
silicone long-life exterior sealant, but butyl
tape is a good alternative that some do-it-yourselfers find easier to
work with. Don’t skimp
on the sealant and be
careful not to seal any
drain holes. Apply sealant to both the sides
and surface of the port,
filling the gap. Do not tighten the port all the
way down. You don’t want to squeeze out all
of the sealant, just enough to ooze around
the edges. Trim up the excess after it cures.
to learn more about which sealant
to pick and for tips on re-bedding
deck fittings and sealing core, see
this article online at
Using a wet
liquid dish soap
outside of the
trim ring of the
port before applying sealant.
the soap will
around the port.
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