• On fin-keel vessels, the transducer should be mounted more
than 300 mm (12 in.) and less than 600 mm (24 in.) in front of
the keel and on or near the centerline.
• On full-keel vessels, the transducer should be mounted in the
center of the ship, away from the keel at the point of
minimum deadrise.
• On single-drive vessels, the transducer must not be mounted
in the path of the propeller.
• On twin-drive vessels, the transducer should be mounted
between the drives, if possible.
• The transducer must be mounted on a flat location at less
than 6° of deadrise angle.
• The transducer should be mounted well ahead of the
propellers and shafts.
• The transducer should be mounted in a location where it is
vertical when the boat is underway. If the transducer leans
forward, the marine bottom can appear to slope upward. If
the transducer leans aft, some surface clutter may appear.
• The transducer should be mounted more than 600 mm
(24 in.) from other transducers.
• The transducer should be mounted in a location that is
unobstructed by the keel or propeller shafts.
• The transducer must be mounted in a location where it is
continuously immersed in water.
• The transducer should be mounted in a location that allows
accessibility to the transducer from the inside of the vessel.
• The transducer should not be mounted behind strakes, struts,
fittings, water intake or discharge ports, or anything that
creates air bubbles or causes the water to become turbulent.
• The transducer should not be mounted in a location where it
might be jarred when launching, hauling, or storing.
• The transducer can cause cavitation that can degrade the
performance of the boat and damage the propeller.
• The transducer must be in clean (non-turbulent) water for
optimal performance.
• If you have a question about the location of the thru-hull
transducer, contact your vessel builder or other owners of
similar vessels for advice.
Tools Needed
• Drill and 3 mm (
1
/
8
in.) bit
• 25 mm (1 in.) hole saw (fiberglass hull)
• 32 mm (1
1
/
4
in.) hole saw (metal hulls)
• Sandpaper
• Masking tape
• Marine sealant
• Slip-joint pliers (metal hulls)
• Metal file (metal hulls)
• Epoxy or exposed core sealant (cored fiberglass hulls)
• Fiberglass cloth and resin (option for sealing a cored-
fiberglass hull)
• Cable ties
Cored Fiberglass Boat Hull Installation
Instructions
Drilling a Hole in a Cored-Fiberglass Hull
1
From inside the boat, drill a 3 mm (
1
/
8
in.) pilot hole
completely through the hull.
2
Examine the pilot hole on the outside of the boat, and select
an option:
• If the pilot hole is not in the correct location, seal the hole
with epoxy and repeat step 1.
• If the pilot hole is in the correct location, use a 25 mm (1
in.) hole saw to cut a hole from the outside of the boat
through the outer fiberglass skin only. Do not cut
completely through the hull.
3
On the inside of the boat, at the pilot hole location, use a hole
saw to cut a hole 9 to 12 mm (
3
/
8
to
1
/
2
in.) larger than the
hole you cut in the outside of the boat in step 2.
Cut through the inner fiberglass skin and most of the core,
without cutting the outer skin.
NOTE:
When cutting the inner fiberglass skin and core, be
careful to not cut the outer fiberglass skin, or you will not be
able to correctly seal the hull.
4
Remove the inner fiberglass skin and core you cut in step 3.
You should be able to see the inside of the outer fiberglass
skin.
5
Sand the inside of the hole and the areas immediately around
both the inside and outside fiberglass skin.
6
Clean the area using a mild detergent or weak solvent, such
as isopropyl alcohol, to remove any dust and dirt.
Preparing a Cored-Fiberglass Hull
NOTICE
If the core of a cored-fiberglass hull is not sealed properly, water
may seep into the core and severely damage the boat.
À
Fiberglass or casting epoxy (not included)
Á
Cylinder spacer (included bushing)
Â
Inner fiberglass skin
Ã
Core
Ä
Outer fiberglass skin
1
Drill the hole through the hull.
2
Seal the core inside the hull using either fiberglass (
) or casting epoxy
(
Sealing the Core with Casting Epoxy
).
2
