Transducer mounts on sailboat hulls can be
tricky because a long keel is more likely to
interfere with the cone-shaped beam as it
expands downward from the transducer. Either
forward or aft of the keel, rather than to either
side of it, is often the best location. Powerboats
with prominent keels can also have this problem.
If you have a side- and/or forward-scanning
unit, it must be mounted on the centerline,
forward of the keel.
Transom-mounted transducers are typi-
cally used on powerboats due to their relative
ease of installation. However, do not place a
transducer directly in front of an engine drive’s
lower unit, where the disturbed water flow
could interfere with engine cooling and might
cause propeller cavitation as well. It is advis-
able to offset it by as much as 18 inches. On
single-engine installations, this means the
transducer will be away from the boat’s center-
line, while on dual-engine installations, the
centerline may be the best location.
Yet another mounting option is to glue the
transducer to the inside of the hull. In most
installing depth sounders, weather systems, and autopilots 159cases, the transducer will transmit and receive its
signal directly through the hull material; in oth-
ers, it is mounted inside a fluid-filled chamber
(usually filled with compass fluid or a 50-50
blend of antifreeze and water), which is mounted
to the inside of the hull. These chambers are
available commercially, but they can also be
home-built from 4-inch ID (inside diameter)
PVC pipe cut to the hull contour and sealed on
top with clear Plexiglas and silicone sealer. It used
to be easier to replace transducers mounted in
this fashion, but with modern adhesives, there’s
no longer much of an advantage.
For an inside-the-hull installation to be
effective, the transducer must rest on a solid
mass of material. Solid GRP (glass-reinforced
plastic—i.e., fiberglass) and wood hulls work
well, but cored laminates do not. Some trans-
ducers may work through some metal hulls,
but it’s advisable to test the transducer first
before making the installation permanent.
Whether a transducer is mounted in a
chamber or to the hull, the transducer face
needs a “solid” surface for its vibrations to beThis transom-mounted transducer on a dual-outboard boat is located to port of the
boat’s centerline to avoid disturbing the water flow to either of the lower units.cabletransducercenterline