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3
Installing
Caution: Never pull, carry, or hold the ultrasonic insert by
the cable as this may sever internal connections.
1. From outside the hull, push the housing into the mounting hole
using a twisting motion to squeeze out excess sealant (see
Figure 3). Align the arrow on the lip of the housing pointing
forward toward the bow. If the sensor is not installed on the
centerline, angle the housing slightly toward the centerline to
align it with the water flow.
2. From inside the hull, slide the washer onto the housing.
Aluminum hull less than 6mm (1/4") thick—Use an
additional rubber, fiberglass, or plastic washer. Never use
bronze since electrolytic corrosion will occur. Never use wood,
since it will swell possibly fracturing the plastic housing.
3. Screw the hull nut in place being sure the notch on the upper rim
of the housing and the corresponding arrow on the lip are still
positioned forward toward the bow (see Figures 3 and 5). (If your
plastic housing has wrenching flats, do not clamp tightly, possibly
causing the housing to fracture.)
Plastic hull nut—Hand-tighten only. Do not over-tighten.
Metal hull nut—Tighten with slip-joint pliers.
Wood hull—Allow the wood to swell before tightening the hull
nut securely.
4. Remove any excess sealant on the outside of the hull to ensure
smooth water flow over the ultrasonic insert.
Warning: The O-rings must be intact and well
lubricated to make a watertight seal.
5. After the sealant cures, inspect the O-rings on the ultrasonic
insert (replace if necessary) and lubricate them with the silicone
lubricant supplied.
Important: For the sensor to work properly, the bottom of the
insert must be flush with the bottom of the housing.
6. Slide the ultrasonic insert into the housing with the arrow on the
top pointing forward toward the bow. Seat it into place with a
pushing twisting motion until the key fits into the notch. The arrow
on the tip of the insert, the notch in the housing, and the arrow on
the lip will be aligned. Be careful not to rotate the housing and
disturb the sealant. Screw the cap nut in place and hand-
tighten only. Do not over-tighten (see Figure 3).
Warning: Always attach the safety wire to prevent the insert
from backing out in the unlikely event that the cap nut fails or is
screwed on incorrectly.
7. Attach the safety wire.
Plastic housing—Attach the safety wire to one eye in the hull
nut. Lead the wire in a counterclockwise direction and thread it
through one eye in the cap nut, along the side of the cap nut,
through the second eye in the cap nut, and the second eye in
the hull nut. Twist the wire securely to itself.
Metal housing—Wrap one end of the safety wire tightly around
the housing and twist it together with the long end. Lead the wire
straight up and through the eye in the cap nut. Loop the wire
back down and twist it securely to itself.
8. To wire the ultrasonic sensor, follow the instructions, “Wiring” on
page 5.
Checking for Leaks
Warning: Never install a thru-hull sensor and leave the boat in the
water unchecked for several days.
When the boat is placed in the water, immediately check around
the thru-hull sensor for leaks. Note that very small leaks may not
be readily observed. It is best not to 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.
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 housing to become loose.
Warning: Always wear safety goggles and a dust mask.
1. Drill a 3mm or 1/8" pilot hole from inside the hull. 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 51mm or 2" hole saw, cut the hole from outside the
hull through the outer skin only (see Figure 5).
3. From inside the hull, use the 60mm or 2-3/8" hole saw to cut
through the inner skin and most of the core. 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 are fully exposed.Sand and clean
the inner skin, core, and the outer skin around the hole.
Caution: Completely seal the hull to prevent water seepage into
the core.
5. If you are skilled with fiberglass, saturate a layer of fiberglass cloth
with a suitable resin and lay it inside the hole to seal and strengthen
the core. Add layers until the hole is the correct diameter.
Alternatively, a hollow or solid cylinder of the correct diameter
can be coated with wax and taped 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 (alcohol) before sanding.
7. Proceed with “Bedding” and “Installing” on page 2.
Figure 4. Preparing a cored fiberglass hull
inner skin
core
outer skinsolid or hollow cylinder
pour in
casting
epoxy
9-12 mm
(3/8-1/2")
larger than the
hole through the
hull’s outer skin
hull thickness