GT51M-TH Thru-Hull Sonar Transducer - CHIRP/ClearVü/SideVü

The Garmin GT51M-TH transducer is a through-hull transducer designed for permanent and robust installation on your vessel’s hull. It delivers consistent, interference-free sonar performance, unlike transom-mount transducers that can be affected by turbulence. Its through-hull installation ensures improved signal quality by avoiding air bubbles and disturbances, which is critical for accurate readings.

Transducer location is critical to optimize GT51M-TH performance. Follow these guidelines:

Outboard and sterndrive vessels: Mount the transducer forward and close to the engine(s).Inboard vessels: Mount it forward and away from the propeller and propeller shaft.Longitudinal-vee hulls: Install it forward of the first vee.High-deadrise hulls: Mount the transducer slightly tilted toward the bow, parallel to the centerline.Slender hulls: Position it 25 cm to 75 cm (10 to 30 in.) forward of the keel and no more than 10 cm (4 in.) from the centerline.Displacement hulls: Install it about one-third of the waterline length from the bow, and 150 mm to 300 mm (6 to 12 in.) off the centerline.In all cases, the transducer must be mounted parallel to the fore-aft axis of the vessel and in an area of clean, non-turbulent water. Avoid placing it behind strakes, frames, fittings, through-hulls, or exhaust outlets—anything that could create air bubbles or turbulence. It must also be clear of the propeller wash.

For best results, ensure the transducer is fully submerged at all times and that the hull area around it remains free of marine growth.

Using a fairing block is recommended if the deadrise angle of your hull at the mounting location exceeds 5°. The fairing block allows the transducer to be positioned parallel to the waterline, significantly improving the accuracy of sonar readings. To determine if a fairing block is necessary, you must measure the deadrise angle at the exact installation point. The block can be cut to match your hull’s deadrise angle, with a maximum cut angle of 25°.

Yes, it is mandatory to update the software of your Garmin chartplotter when installing the GT51M-TH transducer. This update ensures compatibility and optimal performance between the transducer and your navigation device. You can find the software update instructions in the user manual of your Garmin chartplotter.

The Garmin GT51M-TH transducer is designed to be installed on different types of hulls, including:

Fiberglass hulls (with or without core).Metal hulls.However, the installation process and specific tools may vary depending on the material and structure of your hull. Detailed instructions are provided for preparing each type of hull (fiberglass with core, without core, and metal) to ensure correct and secure installation. It is important to consult the installation manual for specifics related to your hull type.

To ensure a perfect seal and prevent water ingress after installing the GT51M-TH transducer, you must apply marine sealant properly. Key points:

Apply marine sealant around the base of the transducer shaft and the anti-rotation bolts before inserting them into the hull. If using a fairing block, also apply marine sealant to the side of the block that will be in contact with the hull’s exterior. Similarly, apply marine sealant to the side of the backing block that will be in contact with the hull’s interior.

After tightening all nuts, remove any excess sealant from the exterior of the fairing block and hull before it cures. This ensures smooth water flow over the transducer.

It is critical to use a flexible, fast-curing marine sealant specifically designed for use below the waterline.

Check the transducer’s alignment and ensure no air bubbles are trapped under the fairing block during installation.