Overview

The Garmin GDT 43 is a thru-hull transducer that measures water depth and water temperature for compatible marine instruments. It runs at 200 kHz, reads depths up to 275 m (900 ft.) depending on conditions, and uses a 43 mm (1 11/16 in.) thru-hull hole size with a 6 m (19.7 ft.) cable.

It also works as a retrofit for existing Nexus and Silva 43 mm thru-hull transducers (TH43), which can save time when you are replacing an older sensor and want to keep the same hull opening. The body is intended for hulls with a 0-20 degree deadrise and supports hull thickness from 6 to 42 mm (0.24 to 1.65 in.).

This is a solid match for sailboats and powerboats that want dependable depth under the keel plus water temperature on the instrument page, whether you are cruising unfamiliar shallows, fishing temperature breaks, or keeping an eye on the seabed while maneuvering in tight harbors.

Key features

• Depth and water temperature sensing in one thru-hull unit
• 200 kHz sonar with depth capability up to 275 m (900 ft.), depending on water conditions and installation
• 43 mm (1 11/16 in.) thru-hull hole size, with support for hull thickness from 6 to 42 mm (0.24 to 1.65 in.)
• 6 m (19.7 ft.) transducer cable for routing to an instrument location
• Intended for hulls with 0-20 degree deadrise
• Retrofit compatibility with Nexus and Silva 43 mm thru-hull transducers (TH43)
• NMEA 2000 network connection available when used with an NMEA 2000 adapter

Variants

This product is offered in multiple configurations based on how you want to connect depth and temperature data to your onboard system.

The sensor form factor remains the same 43 mm thru-hull style; the practical difference is whether the configuration is meant for Nexus wiring or includes an NMEA 2000 adapter for network integration.

• 010-01749-00: Version GDT 43. This version is set up for direct wiring to a compatible Nexus depth port, with cable length trimmed as needed during install.
• 010-01749-10: Version GDT 43 NMEA 2000. This version includes an NMEA 2000 adapter so depth and temperature can be placed on an NMEA 2000 backbone and viewed on compatible displays.

Compatibility and fit

Plan for a 43 mm (1 11/16 in.) hull opening and confirm your hull thickness falls within 6 to 42 mm (0.24 to 1.65 in.). The transducer needs clean, non-turbulent water flow, so placement matters: avoid areas behind strakes, intakes, discharges, or other fittings that introduce aerated water.

On fin-keel sailboats, the recommended placement is forward of the keel while staying close to the centerline; on full-keel vessels, mounting at a slight angle that aims toward the bow is preferred. On powerboats, keep it away from sharp chines and clear of prop wash, especially on single-drive setups.

Installation and setup

Thru-hull installs call for careful hole placement, proper sealing, and inside access to tighten and inspect the fitting. For cored fiberglass, the core around the penetration should be sealed before final assembly to prevent water intrusion. Use marine sealant at the flange, follow cure times, and always do an in-water leak check before leaving the boat unattended.

Electrical and system integration

For Nexus systems, the cable can be cut to length and landed on the dedicated depth port. Wire mapping is: black to black, red to blue, shield to shield, and the white conductor is not used. If the instrument does not show data on first power-up, calibration may be required in the Nexus environment.

For NMEA 2000 installations, the transducer connects through an NMEA 2000 adapter and then into the network via a drop cable and T-connector. The adapter supports 9 to 16 Vdc power input and has a maximum power consumption of 2.4 W.

Maintenance and care

Like any hull sensor, performance drops when marine growth builds up. Clean fouling with a soft cloth and mild detergent, and step up to a scouring pad or putty knife only when growth is heavy. After any cleaning or service, confirm the seal and check for leaks at the installation site.