The Quiet Game
If you're looking for a more tranquil ride next time you're out on the water, it's time to make your engine a little quieter.
July 1, 2005
Whether it's the cringe you get while you're desperately trying to keep quiet getting in and out of
the marina, or the sinking feeling in your gut once you're over your favorite fishing hole and
realize that the fish heard you a mile away ' you know you've officially reached the point where
you're ready to make your I/O sound quieter.
Those of you who have older boats, and some of you that may have new ones that don't have
sound insulation in the engine boxes, should give this a try because it's a relatively simple
project that should take you under two hours, a significant portion of which will be spent waiting
for glue to dry.
Your I/O might not necessarily be louder than anyone else's, which means that it probably
still makes enough noise to make conversation difficult at times. The answer to your problems can
be found in the Noise Reduction Kit, made by a Massachusetts company called Soundown (800/359-1036,
www.soundown.com).
Gearing up
For this project, the only thing you'll need is the I/O kit, which costs under $100 (they
make an outboard kit for under $45). There are also other kits available, some with pre-glued
panels, and other accessories. This particular I/O kit comes with 24 square feet of one-inch-thick,
fire-retardant (not fireproof), foil-faced, sound-deadening foam; a can of spray-on glue; a variety
of fasteners (very sharp ones!); and edge taping.
All you'll need for this job is decent scissors, a utility/razor knife, wrapping paper to
make templates (not a necessity, but it'll make for a better-looking, tighter-fitting job), a pair
of electrician's cutting pliers and some adhesive other than the spray-on glue supplied. For the
latter, you can use a quick-cure polysulfide adhesive that can generally be found at any ship's
store, such as Multi-Caulk Sealant. It's a bit messy
to work with, but you'll have plenty of uses for it beyond this project.
Regarding the edge taping ' substituting 'real' duct tape would work, especially if you
believe in the DIYers adage, 'If it moves, WD-40 it; if it's not supposed to move, duct tape it.'
The foam will suck water, and that's one reason for the edge taping, the other reason being that no
gaps or spaces mean less noise.
Hush, Hush Sweet ...
The first step is scrubbing down the engine box, and then (after it's dried) mounting the
fasteners to the box. For overhead applications, one fastener every two feet is recommended. For a
typical 19-footer's engine box, you can put one in each corner and one in the center, but go with a
few more ' 10 come with the kit, and you won't have to use them on the sides of the box.
Before you do anything else, you need to glue on the fasteners (which look like those old
general store implements with a nail sticking up that you impale receipts on) with the sealant, and
then let them set. Go have coffee, do a crossword puzzle, make an effort to start some chores. Make
sure to wait for the fasteners to set ' otherwise the foam will start to sag, and then you'll have
to redo the job.
Next: Here's where you can opt to template this out, although transferring measurements
directly to the soundproofing is something that can work as well. Measure the surfaces of your
engine box to be covered. The top (and since the engine box is lying upside down, it's the bottom)
is simple, but the sides and lips get slightly more complicated. A good way to go might be with a
big piece for the top, then a strip for any ledges your box may have, another strip to fit over the
rod holders in the engine box (measure the step the rod holders were in and the spacing of the
holders, cut an 'X' for each holder and slip the foam over them). There are separate pieces for the
sides and back.
All in all, it comes out to eight separate pieces. Pre-fit everything after everything has
been cut. Make sure to cut everything a tad long (no more than a half inch), especially where it'll
be joining other pieces.
You may have to think out how you'll get the required pieces out of the sound-proofing
material, but there'll be plenty for your average-size I/O.
Now is when you get to use the spray-on glue. Follow the directions on the can ' which tell
you to spray a light coating of adhesive on the back (not the aluminum side) of the foam, and a
light coating on the engine box. While both are tacky, begin fitting the pieces, starting with the
top first, then working your way to the side pieces. Tape all the seams where pieces meet, as well
as any exposed foam ends.
Aside from actually inhaling the glue (do the spraying where there's good ventilation),
fitting the top piece is the only 'dangerous' part of this operation. The business ends of the
fasteners are about three inches long and sharp. This is what goes through the foam with a round
disk placed over the nail to hold the foam in place; the remainder of the nail projecting past the
keeper is cut off. Be careful pushing the foam on to the fasteners, or you'll end up with a hole in
your hand.
The end result? The engine noise level will definitely be reduced. Of course, there are
additional factors that will influence how much quieter things have become. An engine that's
setting up vibrations through the deck and hull will be harder to quiet down than one that isn't,
and any spacing between your engine box and deck should be closed as much as possible. But if done
correctly, with no space showing between sections, you will notice a decrease in sound level.