Raymarine Transducers, User Manual, Page: 35 / 56

Chapter 2: Installation 29
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 when drilling.
1. Drill a 1/8" (3 mm) pilot hole perpendicular to the waterline from
inside the hull. If there is a rib or strut near the selected mounting
location, drill from the outside (see Figure 2-10 ). If the hole is
drilled in the wrong location, drill a second hole in a better loca-
tion. Apply masking tape to the outside of the hull over the incor-
rect hole and fill it with epoxy.
2. Using a 2" (51 mm) hole saw, cut a hole from outside the hull
through the outer skin only.
3. Using the 2 3/8" (60 mm) hole saw, cut through the inner skin and
most of the core from inside the hull. 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
Note:
The optimal interior hole diameter is affected by the hull’s
thickness and deadrise angle. It must be large enough in diameter to
allow the core to be completely sealed.
4. Remove the plug of core material so the inside of the outer skin
and inner core of the hull is fully exposed. Clean and/or sand the
inner skin, core, and the outer skin around the hole.
CAUTION:
Completely seal the hull to prevent water seepage into the core.
5. Coat a hollow or solid cylinder of the correct diameter with wax
and tape it in place. Fill the gap between the cylinder and hull with
casting epoxy. After the epoxy has set, remove the cylinder (see
Figure 2-11 ).