Overview

The Garmin GT15M-THF is a stainless steel thru-hull transducer for mid-band CHIRP traditional sonar, built for a flush install that keeps drag low and keeps the sonar beam properly oriented.

It runs in the 85 to 165 kHz range and is intended to show clear fish arches, structure, and bottom contours. Depth performance is listed to 1,200 ft in saltwater and 1,900 ft in freshwater, depending on conditions.

This model is offered in tilt-angle versions so the element can sit closer to level once installed, which matters on boats with noticeable hull deadrise.

Key features

• Mid-band CHIRP frequency range: 85 to 165 kHz
• Depth performance listed to 1,200 ft in saltwater and 1,900 ft in freshwater
• Stainless steel thru-hull housing with a flush-mounted profile to reduce drag
• Clear target separation for fish arches, structure, and bottom tracking
• Uses transducer auto-identification for straightforward setup on compatible Garmin displays
• Available in multiple tilt angles to match common hull deadrise ranges

Variants

This transducer is offered in multiple tilt-angle configurations. The tilt angle changes how the element sits in the hull so the sonar beam points more straight down after installation.

The main difference between variants is the supported hull deadrise range. Match the tilt to your boat’s deadrise at the intended mounting location for cleaner returns and better bottom tracking.

• 010-02868-00: 0 degree tilt. Intended for hull deadrise angles from 0 to 7 degrees, where a level element is already close to true.
• 010-02868-01: 12 degree tilt. Intended for hull deadrise angles from 8 to 15 degrees, helping correct beam angle on moderate V hulls.
• 010-02868-02: 20 degree tilt. Intended for hull deadrise angles from 16 to 20 degrees, helping keep the beam closer to vertical on deeper V hulls.

Installation and setup

This is a thru-hull installation, so plan for a clear spot with access on the inside of the hull to tighten the hardware and route the cable. The best results come from mounting in clean water flow, away from strakes, steps, and through-hull fittings that can aerate the water.

Before cutting the hole, measure deadrise where the transducer will sit and match it to the tilt option. After bedding and tightening, confirm the face sits correctly and that the cable is supported so it is not taking vibration loads.

Compatibility and fit

This model is meant for compatible Garmin sonar displays that support transducer auto-identification and mid-band CHIRP traditional sonar. If you are replacing an existing transducer, confirm you have the right connector type and that the sonar channel supports the 85 to 165 kHz range.

A flush thru-hull transducer is a good match for boats that spend time at speed and owners who want consistent bottom tracking without a transom-mount hanging in the flow.

Use cases on board

This is a practical pick for anglers who run nearshore and offshore and want a mid-band view that balances coverage with detail, and for cruising boats that need dependable depth reading while underway. It also suits owners who prefer a clean hull profile over external brackets.

Maintenance and care

Keep the face clean for the best performance. In saltwater, rinse after use when possible and check periodically for marine growth, especially if the boat stays in the water.

As part of routine haul-out checks, inspect the housing for impact marks and confirm the bedding area and hardware remain secure.