SHOOT-THRU-HULL
(20° Transducer Only)
The transducer installation inside a fiberglass hull must be in an area
that does not have air bubbles in the resin or separated fiberglass
layers. The sonar signal must pass through solid fiberglass. A success-
ful transducer installation can be made on hulls with flotation materials
(such as plywood, balsa wood, or foam) between layers of fiberglass if
the material is removed from the chosen area. For example, some
manufacturers use a layer of fiberglass, then a core of balsa wood,
finishing with an outer layer of fiberglass. Removing the inner layer of
fiberglass and the balsa wood core exposes the outer layer of fiberglass.
The transducer can then be epoxied directly to the outer layer of fiber-
glass. After the epoxy cures, the hull is watertight and structurally sound.
Remember, the sonar signal must pass through solid fiberglass. Any air
bubbles in the fiberglass or the epoxy will reduce or eliminate the sonar
signals.
To choose the proper location for thru-hull mounting, anchor the boat in
60 feet of water. Add a little water to the sump of the boat. Plug the
INNER HULL
OUTER HULL
FILL WITH EPOXY
EPOXY TO HULL FIRST
transducer into the sonar unit, turn it on, then hold the transducer over
the side of the boat. Adjust the sensitivity and range controls until a
second bottom echo is seen on the display. (you will need to turn both
automatic and ASP off.) Don’t touch the controls once they’ve been set.
Next, take the transducer out of the water and place it in the water in the
sump of the boat. Observe the sonar signal to see if there is a notice-
able decrease in sensitivity. The second bottom signal may disappear
and the bottom signal may decrease in intensity. Move the transducer
around to find the best location. If the sensitivity control has to be
increased greatly to compensate, then the transducer should be
mounted on the outside of the hull. If not, then mark the location that
shot through the hull the best and follow the instructions on the next
pages for a shoot-thru-hull mounting.
