GT12M-THF 0° Through-Hull CHIRP Mid-Frequency Sonar

The Garmin GT12M-THF transducer is made of brass and is designed to be installed on fiberglass, wood, or composite hulls. It must not be installed on aluminum or steel hulls.

You must not install the GT12M-THF transducer on an aluminum or steel hull because it would create galvanic corrosion. This corrosion can cause water ingress around the transducer and potentially damage your vessel.

To install the GT12M-THF transducer in a solid fiberglass hull, use a 73 mm (2 7/8 inch) hole saw to drill the hole.

Yes, it is mandatory to update the software on your Garmin chartplotter after installing the GT12M-THF transducer to ensure optimal performance and full compatibility with the new device.

During installation, you must apply marine sealant to ensure a perfect watertight seal. Here are the steps:

Apply a 2 mm (1/16 in) layer of marine sealant to the inner flange of the transducer housing where it contacts the hull.Apply marine sealant along the threads of the transducer housing to fill the gap between the threads and the hull. The sealant on the threads should extend about 6 mm (1/4 in) above the inside of the hull to seal and secure the hull nut.

For optimal hydrodynamic and sonar performance, the transducer must be mounted in an area of non-turbulent water. Avoid locations behind ribs, struts, fittings, water intakes or discharges, or any other feature that could create air bubbles or cause water turbulence. It should also not be mounted where it could be shaken during launching, towing, or storage. On single-propulsion boats, ensure it is not in the propeller’s wash path.

The Garmin GT12M-THF, 0 degrees is a through-hull transducer designed for sonar detection. It is specifically suited for installation on hulls with a deadrise angle of 0 to 5 degrees at the installation point, ensuring optimal performance.

The Garmin GT12M-THF transducer is made of brass. This material choice makes it robust for compatible hull types.

The GT12M-THF transducer is compatible with fiberglass, wood, or composite hulls. It is specifically designed for installation on these materials.

No, it is imperative not to install the GT12M-THF transducer on aluminum or steel hulls. The brass in the transducer would cause galvanic corrosion with these materials, which could lead to water ingress and damage to your vessel.

The main difference lies in the manufacturing material and compatibility with hull types. The GT12M-THF is made of brass and is compatible only with fiberglass, wood, or composite hulls. The GT15M-THF, on the other hand, is made of stainless steel and can be installed on all hull types (including aluminum and steel), provided the supplied galvanic isolation components are used for the latter.

This 0-degree transducer is designed for vessels where the hull deadrise angle at the installation point is between 0 and 5 degrees. For optimal performance, it is critical to check the deadrise angle of your hull at the chosen location before installation. You can measure it using a smartphone app, an angle finder, a protractor, a digital level, or by consulting your boat manufacturer.

Yes, to achieve the best possible performance and avoid potential damage to the device or your vessel, installation by a qualified marine installer is strongly recommended.

The standard tools required for installation include:

A drillA 3 mm (1/8 in) drill bitAn adjustable wrench (suitable for nuts up to 75 mm)Marine sealant (flexible, fast-curing, for below the waterline)Mild household detergent or rubbing alcoholSandpaperMasking tapeWaterproof electrical tapeA 73 mm (2 7/8 in) hole saw for solid fiberglass hullsFor sandwich fiberglass hulls, marine epoxy resin is also required.

Yes, a software update for the Garmin chartplotter is required after installing the GT12M-THF transducer to ensure optimal performance. You can find the update instructions in your Garmin chartplotter’s user manual.

For optimal hydrodynamic and sonar performance, the transducer must be mounted in an area of non-turbulent water. Here are some general guidelines:

On outboard and sterndrive boats, it must be mounted forward and close to the engine. On inboard boats, it must be mounted forward and away from the propeller and propeller shaft. On stepped hulls, it must be mounted forward of the first step. It must be mounted parallel to the bow-stern axis of your vessel. Avoid areas behind stringers, bulkheads, seams, water intakes or discharges, or anything that could create air bubbles or cause turbulent water.

For a foam-core fiberglass hull, preparation is crucial to prevent water intrusion:

Drill a 3 mm (1/8 in) pilot hole from the outside of the hull.Use a 73 mm (2 7/8 in) hole saw to cut the transducer hole through the entire hull from the outside.From inside the hull, use a slightly larger hole saw to cut only the inner fiberglass skin and the foam core, ensuring the outer skin is not cut.Seal the core inside the hole using either fiberglass and resin or casting epoxy. This step is essential to prevent water from seeping into the hull core.

During installation, you must apply marine sealant to ensure perfect watertight integrity and prevent water ingress:

Apply a 2 mm (1/16 in) layer of marine sealant to the inner flange of the transducer housing where it contacts the hull. Also apply a layer of marine sealant along the threads of the transducer housing to fill the gap between the threads and the hull. The sealant on the threads should extend approximately 6 mm (1/4 in) above the inside of the hull to seal the assembly and secure the hull nut.

Yes, several precautions are important for the durability and proper operation of the transducer:

Never use the cable to lift or pull the transducer to avoid damaging it.Always operate the transducer when submerged. Operating it in air can damage it due to overheating.For cleaning, do not use solvents such as mineral spirits, acetone, Methyl Ethyl Ketone (MEK), or similar products, as they can cause permanent damage to the transducer's surface. Also, do not use an electric sander or pressure washer.

Yes, the transducer can potentially cause cavitation if the mounting location is not optimal. It is crucial to mount it in an area with clean, non-turbulent water flow. On single-propeller boats, the transducer must not be mounted in the propeller wash path. Cavitation can degrade boat performance and potentially damage the propeller.