GT15M-TH CHIRP Through-Hull Transducer - Mid-Band Frequency

The Garmin GT15M-TH is a thru-hull transducer designed for recreational boaters and anglers. It provides clear seabed definition, precise fish arches, and effective target separation beneath the boat.

The GT15M-TH uses CHIRP Mid-band technology. It operates on a mid-frequency range from 85 to 165 kHz, providing a good balance between wide coverage and detailed target resolution.

This transducer has a power rating of 600 W. It can reach depths of up to 365 meters (1,200 feet) in saltwater and up to 579 meters (1,900 feet) in freshwater.

The GT15M-TH transducer provides depth and water temperature data.

The GT15M-TH transducer has a beam angle of 24°-16° (or 24°-13° depending on the source).

Yes, the GT15M-TH transducer is suitable for both freshwater and saltwater fishing, with specific depth capabilities for each environment (up to 579 meters in freshwater and 365 meters in saltwater).

Yes, thanks to its CHIRP mid-band position, the GT15M-TH is versatile. It offers a good balance between coverage and target resolution, making it suitable for various coastal and moderate offshore fishing conditions.

The GT15M-TH transducer requires a through-hull (thru-hull) installation, meaning it is mounted through the boat's hull for a flush fit.

For installation, you will need:

A drill and a 3 mm (1/8 in) bitA 25 mm (1 in) hole saw for fiberglass hullsA 32 mm (1 1/4 in) hole saw for metal hullsSandpaperMasking tapeMarine sealantA multi-grip pliers (for metal hulls)A metal file (for metal hulls)Epoxy or core sealant (for fiberglass hulls with exposed core)Optionally, fiberglass cloth and resin (to seal a fiberglass hull with core)Cable ties

For a fiberglass hull, a 25 mm (1 inch) hole saw is required. For metal hulls, a 32 mm (1 1/4 inch) hole saw is required.

The transducer must be mounted in a flat location with a tilt angle of less than 6°, continuously submerged in clean (non-turbulent) water, and well ahead of propellers and shafts. It must be more than 600 mm (24 in) away from other transducers and be vertical when the boat is underway. The location must also be accessible from inside the boat.

Installation on a foam-core fiberglass hull requires sealing the core to prevent water intrusion. After drilling a pilot hole, cutting through the outer skin and inner core, the core must be sealed with fiberglass and resin or casting epoxy. It is critical not to cut the outer skin when trimming the inner core.

Yes, on a boat with a deadrise angle greater than 5°, a fairing block must be fabricated (not sold by us) to compensate for the angle and ensure the transducer remains vertical.

Yes, it is important to avoid locations that could create air bubbles or make the water turbulent, such as behind the planks, struts, fittings, water intakes, or discharges. The transducer must also not be mounted in the propeller path for single-engine boats, nor in a location where it could be shaken during launching, towing, or storage.

The GT15M-TH transducer is designed to be compatible with Garmin chartplotters that support CHIRP Mid-band technology. It may be necessary to update your chartplotter's software to ensure optimal compatibility and access to all features.

To update the software, you must download the software bundle corresponding to your chartplotter from garmin.com/support/software/marine.html to a memory card (up to 32 GB, formatted in FAT32) using a Windows computer. Then insert the memory card into the chartplotter after it has fully booted and follow the on-screen instructions.

A memory card with a maximum capacity of 32 GB, formatted as FAT32, is required to load the new software and update the transducer and chartplotter.

Yes, if you do not have a computer running Windows, you can contact Garmin customer support to order a preloaded software update card.

With a fairing block, the transducer can be adapted to hulls up to 29 mm (1.15 in) thick for a 12° beam angle, and up to 19 mm (3/4 in) for a 20° beam angle.