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Stainless steel transducer in a metal hull—To prevent
electrolytic corrosion, the stainless steel anti-rotation bolt must
be isolated from the metal hull. Slide the isolation sleeve over the
bedded anti-rotation bolt as far down as possible (Figure 6).
Apply a 2mm (1/16") thick layer of the marine sealant to the
outside of the sleeve.
2. Apply a 2mm (1/16") thick layer of marine sealant to the side of
the washer that will contact the backing block.
3. Push the anti-rotation bolt through the fairing and the hull.
4. From inside the hull, screw the washer (sealant side down) and
the nut onto the anti-rotation bolt.
Stainless steel transducer in a metal hull—Be sure the
isolation sleeve is between the anti-rotation bolt and the hull
(Figure 6). However, the isolation sleeve must be below the
washer and nut to prevent the sleeve from interfering with
tightening the nut.
5. Use slip-joint pliers to tighten the hull nut. Then tighten the nut
on the anti-rotation bolt. Do not over-tighten, crushing the
fairing or hull.
Cored fiberglass hull—Do not over tighten, crushing the hull.
Wood hull—Allow for the wood to swell before tightening the nut.
6. Use marine sealant to half-fill the hollow in the yellow triangular
plug. Apply a 2mm (1/16") thick layer of marine sealant to the
three sides of the plug that form the triangle. The sealant will
hold the plug firmly within the fairing and fill any gap between
the anti-rotation bolt and the plug.
7. The yellow triangular plug fits one way only. Push the yellow
plug into the recess in the fairing until it is FLUSH with the
outside of the fairing. This will squeeze out excess sealant. If
necessary, tap it into place with a mallet.
NOTE: If the triangular plug is slightly recessed within the
fairing, use sealant to fill the gap. The plug must be FLUSH with
the fairing for good performance.
8. When the boat is underway, especially at high speeds, water
will enter any gaps and push against the fairing with
considerable force, possibly rotating it. Fill any gaps between
the fairing and the hull with marine sealant. If there is any gap
greater than 3mm (1/8"), replace the fairing. Remove the
excess sealant on the outside of the fairing and hull to ensure
smooth water flow under the transducer.
Cable Routing & Connecting
CAUTION: If the sensor came with a connector, do not remove it
to ease cable routing. If a cable must be cut and spliced, use
Airmar's splash-proof Junction Box No. 33-035 and follow the
instructions supplied. Removing the waterproof connector or
cutting the cable, except when using a water-tight junction box,
will void the sensor warranty.
1. Route the cables to the instrument being careful not to tear the
cable jacket when passing it through the bulkhead(s) and other
parts of the boat. Use grommet(s) to prevent chafing. To reduce
electrical interference, separate the transducer cables from
other electrical wiring and the engine. Coil any excess cable and
secure it in place with cable ties to prevent damage.
2. Refer to the instrument owner's manual to connect the
transducer to the instrument.
Checking for Leaks
When the boat is placed in the water, immediately check around the
transducer for leaks. Note that very small leaks may not be readily
observed. Do not leave the boat in the water for more than 3 hours
before checking it again. If there is a small leak, there may be
considerable bilge water accumulation after 24 hours. If a leak is
observed, repeat "Bedding" and "Installing" immediately (see page 4).
Dimension equal to
the thickness of the
hull's outer skin to
ensure adequate
clearance
pour in
casting
epoxy
hull
solid or hollow
cylinder
Figure 7. Preparing a cored fiberglass hull
Copyright © 2005 Airmar Technology Corp.
Installation in a Cored Fiberglass Hull
The core (wood or foam) must be cut and sealed carefully. The
core must be protected from water seepage, and the hull must be
reinforced to prevent it from crushing under the hull nut allowing
the transducer to become loose.
CAUTION: Completely seal the hull to prevent water seeping into
the core.
1. Drill a 3mm or 1/8" pilot hole perpendicular to the waterline from
inside the hull (Figure 7). If there is a rib, strut, or other hull
irregularity near the selected mounting location, drill from the
outside. If the hole is drilled in the wrong location, drill a second
hole in a better location. Apply masking tape to the outside of the
hull over the incorrect hole and fill it with epoxy.
2. Using the appropriate size drill bit or hole saw, cut a hole from
outside the hull through the outer skin only. Be sure to hold the
drill plumb, so the hole will be perpendicular to the water surface.
3. The optimal interior hole diameter is affected by the hull's
thickness and deadrise angle. It must be large enough in
diameter to allow the core to be completely sealed.
Using the appropriate size drill bit or hole saw, cut through the
inner skin and most of the core from inside the hull keeping the
drill perpendicular to the hull. The core material can be very soft.
Apply only light pressure to the hole saw after cutting through the
inner skin to avoid accidentally cutting the outer skin.
4. Remove the plug of core material, so the inside of the outer skin
and the inner core of the hull is fully exposed. Sand and clean
the inner skin, core, and the outer skin around the hole.
5. Coat a hollow or solid cylinder of the correct diameter with wax
and tape it in place. Fill the gap between the cylinder and hull
with casting epoxy. After the epoxy has set, remove the cylinder.
6. Sand and clean the area around the hole, inside and outside, to
ensure that the sealant will adhere properly to the hull. If there
is any petroleum residue inside the hull, remove it with either
mild household detergent or a weak solvent, such as alcohol,
before sanding.
7. Follow the same procedure to prepare the hull for the anti-
rotation bolt. Repeat steps 1 through 6.
8. Proceed with the installation beginning with "Cutting the
Fairing" on page 3. Note that all holes are already drilled.
Anti-fouling Paint
Surfaces exposed to salt water must be coated with anti-fouling
paint. Use water-based anti-fouling paint only. Never use ketone-
based paint since ketones can attack many plastics possibly
damaging the transducer. Reapply anti-fouling paint every 6
months or at the beginning of each boating season.
inner skin
core
outer skin
5
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