Boating USA — February 2018

(Jacob Rumans) #1
BOAT DOCTOR ///WHAT TO LOOK FOR

QUICK TIP


Leaks aboard are a headache, fi guratively, of course. But
selecting between myriad sealants and caulks at the marine
hardware store might cause a literal headache. Before reach-
ing for the OTC analgesic, consider what you’re trying to bond
or seal, and select the right product based on its properties.
—Capt. Vincent Daniello

POLYURETHANE Poly-
urethanes, like 3M 5200, are
best for hardware above and
below the waterline, like cleats
and prop struts, with little need
for removal in the future. Fast
Cure 4200 from 3M, roughly
half as tenacious as 5200,
provides more than enough
adhesion for most applications
above or below the water but
is more easily removed with a
stiff putty knife. (Read about
four solvents you can use to


remove 5200 at boatingmag
.com/marine-solvents-for-
removing-5200.)

POLYETHER AND SMP
Polyurethane yellows in the
sun. Silane-modifi ed polymers
(SMP), like 3M 4000UV, and
polyethers, like Star brite Boat
Caulk or West Marine Multi-
Caulk, off er good adhesion
while still being removable,
but UV rays won’t discolor
them. Skin-over and cure
times are similar to fast-cure
polyurethane.

POLYSULFIDEBoatLife’s
Life-Calk is the sole polysul-
fi de on the market. Its fl exi-
bility, resistance to chemicals,
gas and diesel, plus sunlight

stability make polysulfi de a
good choice for bedding fuel
fi lls and teak decks.

SILICONE AND BLENDS
Silicone is primarily a sealant
— a fl exible, sunlight-resistant
gasket, not a glue. For water-
proofi ng hardware that you
know must come apart again
someday, like navigation
light fi xtures, marine silicone

products from 3M, Star brite,
West Marine and BoatLife are
hard to beat. BoatLife’s Life
Seal is a blend of silicone for
UV resistance and polyure-
thane for better adhesion. The
3M 3000UV is an SMP formu-
lated for less adhesion, specifi -
cally for sealing.

PLASTIC AND PAINT
COMPATIBILITY Silicone
can’t be painted; most other
sealants can. But silicone is
compatible with many plas-
tics; other caulks may not be.
Always read instructions and
always test a sample fi rst.

CAULKS AND


SEALANTS


Push caulking tubes through the bead — don’t drag the bead behind — and then “tool”
the caulk to remove air pockets and smooth it out. A gloved finger wet with just a bit of
mineral spirits or acetone works well on polyurethane, polyether and polysulfide. Water
with just a drop of dish soap does the same for silicone. Or try BoatLife’s new Super
Slick Sealant Smoother, which isn’t solvent-based but works on all sealants.

TOOLING
THE
BEAD

PHOTOS: (COUNTERCLOCKWISE FROM TOP LEFT) COURTESY 3M, COURTESY STAR BRITE (2), COURTESY BOATLIFE, COURTESY 3M

SEAL THE DEAL
Marine sealants and
caulks come in a variety
of types for a variety of
onboard applications.

With the exception of silicones, you can cause many caulks and
sealants to skin over more quickly by using a spray bottle to
apply a light mist of water to the bead. Always read directions.
Free download pdf