Interphase Twinscope Operation Manual page 17

DO NOT install a bronze transducer housing directly into
an aluminum or steel hull because electrolytic corrosion
will occur.
IMPORTANT:
1) Make sure the water flow across the thru-hull
transducer is bubble and turbulence free at all speeds if
good performance is to be achieved.
2) Make sure the transducer has an unobstructed view of
the water ahead and below the boat.
3) On displacement-hull power boats, the transducer
should be mounted relatively close to the center line of
the hull.
4) Mount the transducer in a place which has reasonable
access from inside the vessel since the transducer's
bronze nut will require tightening from inside the hull.
Because the Twinscope scans a 12 degree beam from the
surface ahead to directly below the boat, it is important to
make sure that the transducer is installed so that it will
scan in a vertical direction and not off to either side. The
transducer must be mounted so that it's bronze stem is as
perpendicular to the water line as possible. If necessary,
use a fairing block to properly position the transducer.
Use of a Thru-hull Fairing Bl
Nearly all vessels have some dead rise angle at the
transducer mounting location. If the thru-hull transducer
were mounted directly to the hull, the sound beam would
be tilted off the vertical at the same angle as the dead-rise.
Most thru-hull installations will require a fairing block to
insure the transducer is mounted properly.
A fairing block is typically made of teak, mahogany
wood or plastic and should be placed between the
transducer and hull (both inside and outside) to insure
that the transducer's mounting shaft is perpendicular to
the water's surface. Make the fairing block as smooth as
possible, and not bigger than the transducer's face, to
minimize possible turbulence.
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
equipment and skill required, we suggest that your
professional boatyard install the fairing block.
ock
Suggested Thru-Hull
Transducer Locations
Fin Keel
Displacement Hull -
Both Power and Sail
17
Planing Hull