Garmin M265LH In-Hull CHIRP Transducer, Depth Only, 1 kW, 12-Pin

Overview

The Garmin 010-12380-20 is a 1 kW in-hull CHIRP transducer for depth readings, built around a plastic housing and a 12-pin connection for compatible Garmin sonar inputs.

It runs CHIRP Low from 42 to 65 kHz and CHIRP High from 130 to 210 kHz, with beamwidths of 16° to 25° (low) and 6° to 10° (high). It is rated for depths up to 3,000 ft, and the attached cable is 39 ft long, which is usually enough to reach the helm on mid-size to larger boats without extensions.

This is an in-hull installation that shoots through fiberglass, so the outside of the hull stays smooth and there is no below-the-waterline fitting. It is not recommended for cored-hull vessels, and it needs a solid fiberglass section where the mounting tank can be bonded and kept liquid-tight.

Key features

• 1 kW dual-band CHIRP operation: 42 to 65 kHz (low) and 130 to 210 kHz (high)
• Narrow beam coverage for detail: 16° to 25° (low) and 6° to 10° (high)
• In-hull mounting using a liquid-filled tank, keeping the transducer protected inside the boat and leaving the hull exterior untouched
• Supported deadrise range of 0° to 30° when the tank is cut to match the hull angle
• Depth-only transducer (no speed and no water temperature sensing)
• Garmin 12-pin connector with a 39 ft cable for compatible Garmin chartplotters and sonar modules
• Not recommended for cored-hull vessels; performs best over solid fiberglass with a well-chosen mounting spot

Compatibility and fit

Plan for an accessible, solid fiberglass location inside the hull, commonly in the bilge area, where the surface can be cleaned and prepared for bonding the tank. Avoid spots over coring, voids, stringers, fuel tanks, or areas that trap air, since air and core material can weaken returns or make the bottom reading unstable.

The 12-pin plug is intended for Garmin sonar ports that accept 12-pin transducers. If your system uses a different connector style or a black box with a different input, verify connector compatibility before installation.

Installation and setup

Location matters more with in-hull mounts than with through-hull transducers. A practical approach is to test the transducer at the chosen spot while afloat and compare it to a baseline reading with the transducer over the side, then commit to bonding once you see a steady depth number and a strong bottom trace.

The mounting tank is cut to match the hull deadrise so the beam points straight down, then bonded to a smooth, clean section of hull. After curing, the tank is filled with propylene glycol and the transducer is secured in place with its O-ring gasket. Keep the tank in a cool, ventilated area and route the cable away from engine harnesses and high-current wiring to reduce electrical noise.

If the unit is supplied with a factory connector, do not cut it off for routing. Coil and secure any extra cable so it cannot chafe in the bilge.

Use cases on board

This setup is a strong fit for boats kept on a trailer or lift, and for owners who want capable CHIRP depth performance without a through-hull fitting. It also suits offshore runs and deep-water fishing where bottom tracking matters, provided the hull and mounting location support a clean sonar path.

Maintenance and care

Periodically inspect the tank seal and verify the fill level stays above the hull contact area, especially after seasonal temperature swings or heavy pounding. Keeping the bilge clean and the cable properly supported helps maintain consistent readings over time.

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