Garmin GDT 43 Depth and Temperature Transducer Installation Instructions

GDT™ 43

Installation Instructions

Important Safety Information

WARNING

See the Important Safety and Product Information guide in the
chartplotter or fishfinder product box for product warnings and
other important information.

You are responsible for the safe and prudent operation of your
vessel. Sonar is a tool that enhances your awareness of the
water beneath your boat. It does not relieve you of the
responsibility of observing the water around your boat as you
navigate.

CAUTION

Failure to install and maintain this equipment in accordance with
these instructions could result in damage or injury.

Always wear safety goggles, ear protection, and a dust mask
when drilling, cutting, or sanding.

NOTICE

When drilling or cutting, always check what is on the opposite
side of the surface.

This equipment should be installed by a qualified marine
installer.

To obtain the best performance and to avoid damage to your
boat, you must install the Garmin® device according to these
instructions.

Read all installation instructions before proceeding with the
installation. If you experience difficulty during the installation,
contact Garmin Product Support.

Registering Your Device

Help us better support you by completing our online registration
today.

• Go to my.garmin.com/registration.

• Keep the original sales receipt, or a photocopy, in a safe
place.

Garmin Support Center

Go to support.garmin.com for help and information, such as
product manuals, frequently asked questions, videos, software
updates, and customer support.

Mounting Location Considerations

• On fin-keel vessels À, the transducer should be mounted
more than 25 cm (10 in) and less than 75 cm (30 in) in front
of the keel and less than 10 cm (4 in) to the side of the
centerline.

• On full-keel vessels Á, the transducer should be mounted at
a slight angle that aims at the bow, not parallel to the
centerline.

• On power boats and hulls with chines Â, the transducer
should not be mounted near the edge of sharp hull chines.

• On single-drive boats, the transducer must not be mounted in
the path of the propeller.

• On twin-drive boats, the transducer should be mounted
between the drives, if possible.

• The transducer should be mounted parallel to the bow-stern
axis of your vessel.

• 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

• 43 mm (1 11/16 in.) hole saw

• 52 to 55 mm (2 1/16 to 2 3/16 in.) hole saw (cored-fiberglass
hull installations)

• Marine sealant

• Silicone grease

• Cable cutter

• Metal file (metal-hull installations)

• Fiberglass cloth and resin (option for sealing a cored­fiberglass hull)

• 43 mm (1 11/16 in.) cylinder, wax, tape, and casting epoxy
(option for sealing a cored-fiberglass hull)

Installing the Thru-Hull Transducer

If you are installing the transducer in a cored-fiberglass hull, you
must first prepare the hull (Preparing a Cored-Fiberglass Hull,

page 2).

April 2017

190-02112-02_0C

Use a 43 mm (1 11/

1

the mounting location.
Insert the thru-hull fitting in the hull.

2

Apply marine sealant to the outer flange of the thru-hull fitting

3

and tighten the nut by hand.
Slide both rubber O-rings onto the plug.

4

Apply silicone grease to the outside of the plug.

5

Using a slow, twisting motion, insert the plug into the thru-hull

6

fitting.

Verify that the plug is properly seated into the fitting.

7

Mount the fitting with the pin at a 90 degree angle to the

8

centerline of the boat.
After the marine sealant applied in step 3 has cured, remove

9

the nut and apply sealant on the fitting inside the hull.
Replace the nut and tighten it by hand.

10

After installation of the fitting, replace the plug with the actual

11

transducer.
NOTE: It is recommended that you keep the plug for use

while cleaning or servicing your transducer.
Install the wire locking device onto the transducer.

12

in.) hole saw to cut through the hull at

16

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.

Fiberglass or casting epoxy (not included)

À

Cylinder spacer (not included)

Á

Inner fiberglass skin

Â

Core

Ã

Outer fiberglass skin

Ä

• 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.

On the inside of the boat, at the pilot hole location, use a hole

3

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.

Remove the inner fiberglass skin and core you cut in step 3.

4

You should be able to see the inside of the outer fiberglass
skin.

Sand the inside of the hole and the areas immediately around

5

both the inside and outside fiberglass skin.
Clean the area using a mild detergent or weak solvent, such

6

as isopropyl alcohol, to remove any dust and dirt.

Sealing the Hull with Fiberglass

From inside the boat, coat a layer of fiberglass cloth with

1

fiberglass resin and place it inside the hole to seal the core.
Add layers of fiberglass cloth and resin until the hole is the

2

correct diameter of 43 mm (1 11/
After the fiberglass has hardened, sand and clean inside and

3

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/
as the epoxy sets.

Coat a 43 mm (1 11/

1

Insert the cylinder in the hole through the outer skin and tape

2

it in place on the outside of the boat.
Fill the space between the cylinder the core with casting

3

epoxy.
After the epoxy has hardened, remove the cylinder, and sand

4

and clean inside and around the hole.
The cored-fiberglass hull is now prepared, and you can

complete the transducer installation.

in.) cylinder with wax.

16

in.).

16

in.) to act as a spacer

16

NMEA 2000® Connection

The GDT 43 transducer connects to the NMEA 2000 network
through the NMEA 2000 adapter.

Drill the hole through the hull.

1

Seal the core inside the hull using either fiberglass (Sealing

2

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

From inside the boat, drill a 3 mm (1/8 in.) pilot hole

1

completely through the hull.
Examine the pilot hole on the outside of the boat, and select

2

an option:

2

gWind™ Wireless 2 transducer

À

GNX™ Wind instrument

Á

NMEA 2000 adapter

Â