Interphase Color Twinscope Operation Manual page 17

After cutting the fairing block, trial fit the block to the
hull. It is very important that the flat top surface of the
transducer be parallel to the water. Because of the skill
required, we suggest that your professional boatyard
provide the fairing block.
Installing the Thru-hull Transducer
1) Drill a 1/8" pilot hole from inside the hull to assure
access to tighten the housing nut and clearance for the
transducer cables. If there is any hull irregularity near
the selected mounting location, it may be desirable to
drill from the outside.
2) Use a 1-1/16" hole saw and drill the hole from the
outside of the hull. Sand or clean the area around the
hole, inside and outside to insure that the sealing
compound will adhere properly to the hull. Select a
marine grade adhesive sealant, such as 3M 5200, and
use according to the instructions.
3) Remove the bronze hex nut from the housing and
cable.
4) Uncoil the transducer cable and thread it through the
hole into the inside of the hull.
DANGER: DO NOT apply tension to the transducer
cables as this may sever internal connections.
5) Apply a 1/8" thick layer of sealant on the upper flat
surface of the transducer, bronze alignment pin and
fairing block (if used).
6) From the outside of the hull, push the housing into
the 1" hole. Twist the housing slightly to squeeze out
excess sealant. Carefully confirm that the transducer is
aligned so that the round front end is pointed directly
toward the front of the boat.
7) Install and tighten the bronze hex nut (allow for
swelling in wooden hulls).
8) Remove excess sealant from the outside to assure
smooth water flow over the transducer.
DANGER: Wood hulls and fairing blocks will expand
after the boat is put back into the water, so it is
important that the transducer be only hand-tightened
until the wood fully expands. Otherwise the wood
fairing block may crack.
DANGER: Be sure to check for leaks when the boat is
placed in the water. Allow at least 24 hours after
installation for any leak to appear.
DANGER: If the boat is kept in saltwater it is
recommended that the transducer be coated with an
anti-fouling paint. USE ONLY WATER BASED
ANTI-FOULING PAINT. DO NOT USE KETONE
BASED PAINTS. Ketone based anti-fouling paint will
attack the plastic materials used in the transducer. See
the maintenance section on page 38 for
recommendations.
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