Garmin GT15M-IH - User Manual

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GT15M-IH

INSTALLATION INSTRUCTIONS

Mounting Considerations

• The transducer should be mounted over solid fiberglass hulls only, up to 16 mm (

in.) thickness.

• On single thickness fiberglass hulls, the transducer should be mounted in the bilge area near the keel and

transom.

• The transducer should not be mounted aft of the water pickup and other protrusions.

• The transducer should not be mounted over a strake.

• The transducer should be mounted over solid fiberglass, with no dead air space or coring in the boat hull.

• The transducer should be mounted as flat as possible in the boat hull.

• You can refer to the Transducer Placement Guide at garmin.com/manuals/gt15mih for more information

about transducer placement.

Tools Needed

• #1 Phillips screwdriver

• 220-grit sandpaper

• Marine-grade adhesive suitable for the mounting location material

• RV/marine antifreeze fluid or mineral oil

• Rubbing alcohol

Deadrise Angle

Deadrise is the angle formed between a horizontal line and a boat hull at a single point. You can measure the

deadrise angle with a smartphone application, an angle finder, a protractor, or a digital level. You can also ask

your boat manufacturer for the deadrise angle of the specific point on your boat hull.

NOTE: A boat may have several deadrise angles depending on the shape of the hull. Measure the deadrise angle

only at the location where you plan to install the transducer.

In-Hull Tank Considerations

• On a boat hull with a deadrise angle between 0 and 3 degrees, you must install the tank labeled 0°.

• On a boat hull with a deadrise angle between 4 and 8 degrees, you must install the tank labeled 5°.

• On a boat hull with a deadrise angle between 9 and 16 degrees, you must install the tank labeled 12°.

• On a boat hull with a deadrise angle between 17 and 25 degrees, you must install the tank labeled 20°.

GUID-207A1A37-3DE8-4599-8C50-1FC69CCA701F v6December 2023

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Summary

Mounting Considerations

Hull Material and Thickness

Transducer mounts on solid fiberglass hulls up to 16mm thick.

Transducer Placement Guidelines

Avoid mounting near water pickups, protrusions, or strakes; ensure flat mounting.

Additional Placement Resources

Refer to the Transducer Placement Guide at garmin.com/manuals/gt15mih.

Tools and Materials Needed

Essential Tools and Adhesives

Requires Phillips screwdriver, sandpaper, marine-grade adhesive, and antifreeze fluid.

Deadrise Angle Explanation

Measuring Deadrise Angle

Angle between horizontal line and hull. Use smartphone app, angle finder, or ask manufacturer.

In-Hull Tank Selection by Deadrise

Select tank (0°, 5°, 12°, 20°) based on hull deadrise angle for optimal installation.

Installation Process

Testing the Mounting Location

Test transducer feedback in water before permanent mounting. Repeat if necessary.

Installing the In-Hull Tank

Sand, clean, apply adhesive, place tank level with waterline, align with keel arrow.

Mounting the Transducer

Insert O-ring, fill tank with fluid, insert transducer, align notch, secure with screws.

Specifications

Performance Specifications

Details transmit power, maximum depth, frequency range, and operating temperatures.

Summary

Mounting Considerations

Hull Material and Thickness

Transducer mounts on solid fiberglass hulls up to 16mm thick.

Transducer Placement Guidelines

Avoid mounting near water pickups, protrusions, or strakes; ensure flat mounting.

Additional Placement Resources

Refer to the Transducer Placement Guide at garmin.com/manuals/gt15mih.

Tools and Materials Needed

Essential Tools and Adhesives

Requires Phillips screwdriver, sandpaper, marine-grade adhesive, and antifreeze fluid.

Deadrise Angle Explanation

Measuring Deadrise Angle

Angle between horizontal line and hull. Use smartphone app, angle finder, or ask manufacturer.

In-Hull Tank Selection by Deadrise

Select tank (0°, 5°, 12°, 20°) based on hull deadrise angle for optimal installation.

Installation Process

Testing the Mounting Location

Test transducer feedback in water before permanent mounting. Repeat if necessary.

Installing the In-Hull Tank

Sand, clean, apply adhesive, place tank level with waterline, align with keel arrow.

Mounting the Transducer

Insert O-ring, fill tank with fluid, insert transducer, align notch, secure with screws.

Specifications

Performance Specifications

Details transmit power, maximum depth, frequency range, and operating temperatures.

This document provides installation instructions and specifications for the Garmin GT15M-IH in-hull transducer.

Function Description

The Garmin GT15M-IH is an in-hull transducer designed to provide sonar feedback for chartplotters or fishfinders. It operates by transmitting and receiving sonar signals through the boat's hull, eliminating the need for external mounting that could be subject to damage or drag. The transducer is installed within a tank filled with a fluid (RV/marine antifreeze or mineral oil) to ensure optimal signal transmission through the hull. This setup is particularly suitable for solid fiberglass hulls, allowing for a clean installation without hull penetration.

Important Technical Specifications

Transmit Power: 600 W (RMS)
Maximum Depth: 549 m (1800 ft.), dependent on water conditions.
Frequencies: Operates within a range of 85 to 165 kHz, dependent on the chartplotter or fishfinder model.
Operating Temperature Range: 0° to 50°C (32° to 122°F).
Storage Temperature Range: -40° to 70°C (-40° to 158°F).
Hull Thickness Compatibility: Suitable for solid fiberglass hulls up to 16 mm (5/8 in.) thick.
Deadrise Angle Compatibility: The system accommodates various hull deadrise angles through the use of specific tanks:
- 0° tank for 0-3° deadrise.
- 5° tank for 4-8° deadrise.
- 12° tank for 9-16° deadrise.
- 20° tank for 17-25° deadrise.

Usage Features

The GT15M-IH transducer is designed for in-hull mounting, which offers several advantages:

Protection: Being mounted inside the hull, the transducer is protected from marine growth, impact, and damage that external transducers might face.
No Drag: It does not create additional drag on the boat, which can be beneficial for speed and fuel efficiency.
Easy Installation: While requiring careful placement, the installation process involves adhering a tank to the hull and then placing the transducer inside, avoiding the need for drilling through the hull.
Optimal Signal Transmission: The use of a fluid-filled tank ensures good acoustic coupling between the transducer and the hull, facilitating efficient signal transmission and reception.

Maintenance Features

Fluid-Filled Tank: The transducer operates within a tank filled with RV/marine antifreeze fluid or mineral oil. This fluid is crucial for signal transmission and should be maintained.
O-ring Seal: An O-ring is used to seal the transducer within the tank, preventing fluid leakage and ensuring proper operation.
Cleaning: The mounting location on the hull requires thorough cleaning with alcohol and sanding with 220-grit sandpaper before adhesive application to ensure a strong bond.
Adhesive: Marine-grade adhesive is used to secure the tank to the hull, requiring a dry and clean surface for proper adhesion.

Installation Process

The installation involves several key steps:

Mounting Location Selection: The transducer must be mounted on solid fiberglass hulls (up to 16 mm thick), preferably in the bilge area near the keel and transom, away from water pickups, other protrusions, and strakes. It should be mounted as flat as possible and not over any dead air space or coring.
Deadrise Angle Measurement: The deadrise angle of the hull at the chosen mounting location must be accurately measured using tools like a smartphone application, angle finder, protractor, or digital level. This measurement determines which specific in-hull tank (0°, 5°, 12°, or 20°) to use for the most level transducer installation.
Testing the Mounting Location: Before permanent installation, the transducer should be temporarily placed in a plastic bag filled with water and positioned on the wet hull surface. Its performance is then observed on the chartplotter or fishfinder to ensure proper function. If performance is unsatisfactory, a new location must be chosen and retested.
Tank and Transducer Installation:
- The tested mounting location is sanded with 220-grit sandpaper and cleaned with alcohol.
- Marine-grade adhesive is applied to the bottom of the selected in-hull tank.
- The tank is placed in the hull, ensuring its top is level with the water line and an arrow on the tank points to the boat keel.
- Once the adhesive is dry, an O-ring is inserted into the tank's groove.
- The tank is filled with RV/marine antifreeze fluid or mineral oil.
- The transducer is inserted into the tank, aligning its arrow with a notch on the tank.
- The transducer is secured to the tank using enclosed screws, taking care not to overtighten them.
- Finally, the cable is routed and connected to the chartplotter or fishfinder.

The GT15M-IH is a robust solution for boat owners seeking reliable sonar performance without compromising hull integrity or aesthetics.

Garmin GT15M-IH Specifications

General

Brand	Garmin
Model	GT15M-IH
Category	Transducer
Language	English

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