GT17M-THF 0° CHIRP through-hull transducer

The Garmin GT17M-THF 0-degree transducer features a stainless-steel housing and is compatible with a wide range of hull materials. It can be installed on fiberglass, wood, composite, aluminum, and steel hulls. For aluminum or steel hulls, it is critical to use the included galvanic isolation components to prevent corrosion and potential water ingress.

Deadrise angle is the measurement of the angle between a horizontal line and the hull’s outer surface at a given point. For optimal transducer performance, the transducer’s angle must match the hull’s deadrise angle as closely as possible at the installation location.

The Garmin GT17M-THF 0-degree transducer is specifically optimized for hulls with a deadrise angle of 0 to 5 degrees. Garmin offers other GT17M-THF models with 12- or 20-degree angles to suit hulls with different deadrise angles. It is recommended to check your hull’s deadrise angle before drilling holes.

When installing the GT17M-THF transducer on an aluminum or steel hull, it is mandatory to use the included galvanic isolation components. Failure to follow this instruction will result in galvanic corrosion that could cause water ingress around the transducer and damage the hull. These components are designed to electrically isolate the transducer from the metal hull, preventing the electrochemical reaction.

To install the Garmin GT17M-THF transducer, you will need the following tools:

A drillA 3 mm (1/8 in) drill bitA wrench suitable for nuts up to 108 mm (4 1/4 in)A 4.5 mm (3/16 in) Allen keyMarine sealant (flexible, fast-curing, for below the waterline)Mild household detergent or rubbing alcoholSandpaperMasking tapeWaterproof electrical tapeA 98 mm (3 7/8 in) hole saw for fiberglass hulls (solid or cored)A 101 mm (4 in) hole saw for metal hullsGrommets and water-based antifouling paint may also be required depending on the installation.

For optimal performance, the transducer must be installed in an area of clean, non-turbulent water. Here are some general considerations:

General location: The transducer should be mounted forward and close to the engine (for outboards/sterndrives) or away from the propeller and engine shaft (for inboards). Avoid obstacles: Do not install it behind strakes, transoms, fittings, water intake or discharge ports, or anything that could create air bubbles or cause turbulent water.Alignment: Mount the transducer parallel to the bow-to-stern axis of your vessel.Specific hulls: For vee hulls, install it ahead of the first vee. For full-keel hulls, mount it slightly angled toward the bow, parallel to the centerline. For fin-keel hulls, at 25–75 cm ahead of the keel and max 10 cm to the side of the centerline.Propellers: On single-screw boats, do not mount the transducer in the propeller wash. On twin-screw boats, mount it if possible between the propellers.

Yes, it is mandatory to update the software of your Garmin chartplotter when you install this depth sounder. This ensures compatibility and proper operation between the depth sounder and your Garmin device. You can find the update instructions in the user manual of your chartplotter.

Preparing a cored-fiberglass hull is critical to prevent water intrusion. Follow these steps:

Drill a 3 mm (1/8 in) pilot hole from the hull exterior.Apply masking tape around the pilot hole on the exterior to reduce gelcoat cracking.Use a 98 mm (3 7/8 in) hole saw to cut the depth sounder hole through the entire hull from the exterior.From the hull interior, use a slightly larger hole saw to cut only the inner fiberglass skin and core, ensuring the outer skin remains intact.Seal the core inside the hull using fiberglass resin or casting epoxy. For epoxy, use a 98 mm waxed cylinder as a spacer during curing.Once cured, sand and clean the interior and around the hole.Incorrect core sealing can lead to severe boat damage.

To ensure the longevity and performance of your Garmin GT17M-THF transducer, follow these maintenance guidelines:

Leak check: After launching your boat, always check for leaks around the screw holes or the transducer.
Operation: The transducer must always be submerged in water to function properly. Using it out of the water can damage it due to overheating.
Cleaning: Never use solvents such as mineral spirits, acetone, MEK, or similar products to clean the transducer surface. Do not use an electric sander or pressure washer either.
Antifouling paint: If needed, you can apply water-based antifouling paint to the transducer to prevent corrosion and fouling. Do not use any other type of paint.

The Garmin GT17M-THF transducer has a stainless steel housing, providing high durability and optimal resistance to demanding marine environments.

The required mounting hole dimensions depend on your hull material:

For a solid fiberglass hull or a fiberglass hull with a core, a 98 mm (3 7/8 in) hole is required. For a metal hull (aluminum or steel), a 101 mm (4 in) hole is required. These dimensions are critical for proper installation.

Yes, it is possible to apply a water-based antifouling paint to the transducer to prevent corrosion and marine growth. It is important to use only water-based antifouling paint and avoid solvents.

The Garmin GT17M-THF transducer is designed for installation on a wide range of hull materials, including fiberglass, wood, composite, aluminum, and steel.

The Garmin GT17M-THF 0-degree transducer is optimized for hulls with a deadrise angle between 0 and 5 degrees. For different deadrise angles, Garmin offers other GT17M-THF models with 12- or 20-degree angles, allowing precise adaptation to each vessel's geometry.

Yes, when installing the GT17M-THF depth sounder on an aluminum or steel hull, it is mandatory to use the included galvanic isolation components. This feature is critical to prevent galvanic corrosion, which could lead to water ingress around the transducer and damage the hull.

Yes, to ensure optimal performance and avoid any risk of injury, damage to the device, or damage to the vessel, installation by a qualified marine installer is strongly recommended.

To avoid permanently damaging the depth sounder’s surface, do not use solvents such as white spirit, acetone, methyl ethyl ketone (MEK), or similar products. Avoid using an electric sander or a pressure washer for cleaning.

Do not install the transducer behind ribs, frames, fittings, water intake or outlet openings, or any other element that could create air bubbles or turbulent water. The transducer must be in clean, non-turbulent water for optimal performance. Avoid installing it near the engine or in the engine room to prevent interference with the sonar signal and overheating risks.

After physically installing the depth sounder, it is crucial to update the Garmin chartplotter software. Detailed instructions for the update are available in your chartplotter's user manual. Additionally, once the boat is in the water, it is recommended to check for any leaks around the transducer before leaving the boat submerged for an extended period.

Yes, it is mandatory to apply marine sealant along the water path to ensure a perfect seal between the depth sounder and the hull. This includes applying a 4 mm (1/8 in) layer of sealant on the internal flange of the depth sounder and a layer around the depth sounder housing where it will contact the sides of the hole in the hull.

For the installation of the GT17M-THF transducer, you will need the following tools:

A drill with a 3 mm (1/8 in) bitA 98 mm (3 7/8 in) hole saw for fiberglass hulls or a 101 mm (4 in) hole saw for metal hullsA wrench suitable for nuts up to 108 mm (4 1/4 in)A 4.5 mm (3/16 in) Allen keyMarine sealant (flexible, fast-curing type for below the waterline)Mild detergent or rubbing alcohol, sandpaper, masking tape, waterproof electrical tape (optional)Eyelets (optional) and water-based antifouling paint (optional)