
1Use a 43 mm (1 11/16 in.) hole saw to cut through the hull at
the mounting location.
2Insert the thru-hull fitting in the hull.
3Apply marine sealant to the outer flange of the thru-hull fitting
and tighten the nut by hand.
4Slide both rubber O-rings onto the plug.
5Apply silicone grease to the outside of the plug.
6Using a slow, twisting motion, insert the plug into the thru-hull
fitting.
7Verify that the plug is properly seated into the fitting.
8Mount the fitting with the pin at a 90 degree angle to the
centerline of the boat.
9After the marine sealant applied in step 3 has cured, remove
the nut and apply sealant on the fitting inside the hull.
10Replace the nut and tighten it by hand.
11After installation of the fitting, replace the plug with the actual
transducer.
NOTE: It is recommended that you keep the plug for use
while cleaning or servicing your transducer.
12Install the wire locking device onto the transducer.
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.
ÀFiberglass or casting epoxy (not included)
ÁCylinder spacer (not included)
ÂInner fiberglass skin
ÃCore
ÄOuter fiberglass skin
1Drill the hole through the hull.
2Seal the core inside the hull using either fiberglass (Sealing
the Hull with Fiberglass, page 2) or casting epoxy (Sealing
the Core with Casting Epoxy, page 2).
Drilling a Hole in a Cored-Fiberglass Hull
1From inside the boat, drill a 3 mm (1/8 in.) pilot hole
completely through the hull.
2Examine 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 43 mm (1
11/16 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.
3On 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.
4Remove the inner fiberglass skin and core you cut in step 3.
You should be able to see the inside of the outer fiberglass
skin.
5Sand the inside of the hole and the areas immediately around
both the inside and outside fiberglass skin.
6Clean the area using a mild detergent or weak solvent, such
as isopropyl alcohol, to remove any dust and dirt.
Sealing the Hull with Fiberglass
1From inside the boat, coat a layer of fiberglass cloth with
fiberglass resin and place it inside the hole to seal the core.
2Add layers of fiberglass cloth and resin until the hole is the
correct diameter of 43 mm (1 11/ 16 in.).
3After the fiberglass has hardened, sand and clean inside and
around the hole.
The cored-fiberglass hull is now prepared, and you can
complete the transducer installation.
Sealing the Core with Casting Epoxy
To properly seal the core with casting epoxy, you must create a
cylinder with a diameter of 43 mm (1 11/ 16 in.) to act as a spacer
as the epoxy sets.
1Coat a 43 mm (1 11/ 16 in.) cylinder with wax.
2Insert the cylinder in the hole through the outer skin and tape
it in place on the outside of the boat.
3Fill the space between the cylinder the core with casting
epoxy.
4After the epoxy has hardened, remove the cylinder, and sand
and clean inside and around the hole.
The cored-fiberglass hull is now prepared, and you can
complete the transducer installation.
NMEA 2000® Connection
The transducer connects to the network on your vessel. The
GDT 43 connects to the NMEA 2000 network through the thru-
hull Intelliducer™ device.
ÀThru-hull Intelliducer
ÁGDT 43 transducer
2