GARMIN GSD 28 Sonar Module Installation Guide

: September 4, 2024
: Garmin

Table of Contents

GARMIN GSD 28 Sonar Module
Important Safety Information
Installation Preparation
Tools Needed
Mounting the Sonar Module
Connecting the Device to Power
Transducer Wire Color Tables
Specifications
Read User Manual Online (PDF format)
Download This Manual (PDF format)
2 Phillips screwdriver

GARMIN GSD 28 Sonar Module

Important Safety Information

WARNING

See the Important Safety and Product Information guide in the product box for product warnings and other important information.
Failure to follow these warnings, cautions, and notices could result in personal injury, damage to the vessel or device, or poor product performance.
You are responsible for the safe and prudent operation of your vessel. A sonar is a tool that enhances your awareness of the water beneath your boat. It does not relieve you of the responsibility of observing the water around your boat as you navigate.

CAUTION

To avoid possible personal injury, always wear safety goggles, ear protection, and a dust mask when drilling, cutting, or sanding.
To avoid possible personal injury or damage to the device and vessel, disconnect the vessel’s power supply before beginning to install the device.
To avoid possible personal injury or damage to the device or vessel, before applying power to the device, make sure that it has been properly grounded, following the instructions in the guide.
To avoid possible personal injury or damage to this device and vessel, only install this device when the vessel is on land, or when properly secured and docked in calm water conditions.
For the best possible performance and to avoid potential injury, damage to the device, or damage to your vessel, installation by a qualified marine installer is recommended.

NOTICE

When drilling or cutting, always check what is on the opposite side of the surface to avoid damaging the vessel.
Read all installation instructions before proceeding with the installation. If you experience difficulty during the installation, contact Garmin Support.

Transducers
A transducer is required to send and receive a sonar signal from the sonar module. Proper transducer selection and installation are critical to the operation of the device. Because mounting locations vary, see your local Garmin dealer or contact Garmin Support for more information. Go to garmin.com/transducers to select a transducer.

Installation Preparation

Because every boat is different, you must carefully plan the GSD 28 sonar module installation.

Select a mounting location.
Mount the sonar module.
Connect the sonar module to the transducer.
Connect the sonar module to power.
Connect the sonar module to the network.

Tools Needed

Drill
5mm (13/64 in.) drill bit for the mounting surface
2 Phillips screwdriver
3 mm flat screwdriver
Dielectric grease
Wire cutter
Wire stripper
1 in. (24 mm) wrench
Cable ties (optional)
Cable grommets (optional)
Marine sealant (optional)

Replacing a GSD 26 Sonar Module
If you are upgrading from a GSD 26 sonar module, observe these considerations.

The GSD 28 device is horizontally smaller than the GSD 26 device. If possible, you should reuse two of the mounting holes on the right or left side of the mounting surface and drill two new holes for the opposite side. Both models use the same size mounting screws.
You can use the included Garmin BlueNet to Garmin Marine Network adapter and the existing network cable to connect the GSD 28 device to a legacy Garmin Marine Network device on your network (Networking Considerations,).

Mounting the Sonar Module

Mounting Location Considerations

You must mount the sonar module in a location where it cannot be submerged.
You must mount the sonar module in a location with adequate ventilation where it will not be exposed to extreme temperatures.
You should mount the sonar module so that the LEDs are visible and the power and network cables can be easily connected.
You should mount the sonar module in a location within reach of your transducer cable. If required, transducer extension cables are available through your Garmin dealer.

Mounting the Device
NOTICE
If you are mounting the device in fiberglass, when drilling the pilot holes, use a countersink bit to drill a clearance counterbore through only the top gel-coat layer. This will help to avoid cracking in the gel-coat layer when the screws are tightened.
NOTE: Screws are included with the device, but they may not be suitable for the mounting surface.
Before you mount the device, you must select a mounting location and determine what screws or other mounting hardware are needed for the surface.

Trim the template and make sure it fits in the location where you want to mount the device.
Secure the template to the selected location.
Mark pilot holes for the four corners of the device, and remove the template.
Using a 5mm (13/64 in.) drill bit, drill one of the pilot holes and lightly secure the device using one of the screws or selected mounting hardware.
Verify the positions of the other pilot hole marks and adjust them as necessary.
Drill the remaining pilot holes.
Secure the device to the mounting location using the remaining screws or selected mounting hardware.

Sonar Module Connections
NOTICE
Do not force a cable into its port. Forcing the cable can damage the pins. If the cable is properly aligned, the cable should connect easily.
Before you connect the sonar module to the transducer, network, and power, you must mount the sonar module (Mounting the Sonar Module,).

Cable Routing Grommets
When routing cables through your boat, it may be necessary to drill holes to route the cables. Cable routing grommets can be used to cover cable installation holes. The grommets do not create a waterproof seal. If necessary, apply a marine sealant after installation to weatherproof the grommet and the cable. You can purchase grommets from your Garmin dealer or directly from Garmin at garmin.com.

Connecting the Device to a Transducer

WARNING
To avoid the risk of serious injury, make sure the device is not connected to power before removing the terminal block lid.
NOTICE
The cord grips on the GSD 28 come with plugs installed. To ensure water cannot enter the transducer wiring block area and damage the device, do not remove the plug from an unused cord grip, and tighten all locking rings.
The terminal blocks are not removable.

Preparing the Cables to Connect to the Sonar Module
Before you can begin the installation, you must check your transducer compatibility.
NOTE: The device does not support water-speed wheels.

Remove the terminal block lid from the sonar module, using a #2 Phillips screwdriver.
Loosen one of the cord grips, and remove the rubber plug.
If necessary, push the plug all the way through, and retrieve it from inside the terminal block area.
NOTE: When connecting two single-element transducers, you should use the transducer cord grip on the left for a low-frequency transducer and the transducer cord grip on the right for a high-frequency transducer.
Feed the transducer cable through the cord grip, and pull the cable into the terminal block area.

NOTE: If your transducer has a connector, cut the cable as close to the connector as possible, before feeding it through the cord grip. Then, use a wire stripper to remove about 90 mm (3 1/2 in.) of the outer cable jacket and foil shield, 6 mm ( 1/4 in.) of the insulation from each internal wire. Tinning stripped wires is recommended.

Connecting the Wires to the Terminal Block
Before you connect the wires, consult the wiring diagrams (Transducer Wiring Diagrams,) to select the proper wiring configuration for your transducer and the wiring tables (Transducer Wire Color Tables for specific examples of Garmin wire colors.

Connect the uninsulated section of each wire to the terminal block using a 1/8 in (3 mm) flat screwdriver.
NOTE: When connecting two single-element transducers, you must connect the second transducer to the duplicate set of connections on the opposite side of the terminal block.
TIP: The primary transducer cable wire housing covers the wiring bundles. To identify the wiring groups in the bundles more easily, you can remove up to an inch of the cable housing.
If the transducer has a separate outer shield bare wire, connect it to one of the two ground posts under the terminal block using a #2 Phillips screwdriver.

Connecting a Transducer for Manual Configuration
While most transducer models are detected and configured automatically, in some cases you may need to configure a transducer manually.

Connect the temperature wire to the TEMP terminal, or install a jumper wire between the TEMP terminal and the GRND terminal.
For dual-element transducers, install another jumper wire between the TEMP terminal and the GRND terminal on the opposite end of the terminal block.
Connect the remaining transducer wires according to the wire color table (Transducer Wire Color Tables,).
After the sonar module is powered on and connected to the network, configure the transducer using a connected chartplotter (Manually Configuring a Transducer,).

Securing the Wire Connections

When the wire connections are secure, use a 1 in. (24 mm) wrench to tighten the cord grip nut around the transducer cable.
When tightened correctly, you should not be able to pull the transducer cable out of the housing.
Tighten any unused cord grip to form a seal around the rubber plug.
Reinstall the terminal block lid.

NOTE: The sonar module does not operate when the lid is removed.

Connecting the Device to Power

WARNING
When connecting the power cable, do not remove the in-line fuse holder. To prevent the possibility of injury or product damage caused by fire or overheating, the appropriate fuse must be in place as indicated in the product specifications. Connecting the power cable without the appropriate fuse in place voids the product warranty.

Route the cables using the appropriate tie wraps, fasteners, and sealant to secure the cables along the route and through any bulkheads or to the deck.
NOTE: If necessary, the power cable can be extended (Power Cable Extensions, page 5).
Connect the bare-wire end of the power cable to your power source and to the ground.
NOTE: If you have both a 12 Vdc and a 24 Vdc system on the vessel, you should connect the device to the 24 Vdc system for the best performance.
Apply dielectric grease to the connector on the power cable.
Align the notch on the end of the power cable with the POWER port on the device, and press the cable into place.
Tighten the locking ring.

Power Cable Extensions
If necessary, you can extend the power cable using the appropriate wire gauge for the type of power source and the length of the extension. Use marine-grade connectors or solder and water-resistant heat-shrink tubing when extending the power wires.

1 Splice

Power Cable Extension Wire Gauge Table
To find the wire gauge you should use, cross-reference the length of the extension with the voltage of your power supply.

	24 Vdc	12 Vdc
Up to 4.6 m (15 ft.)	10 AWG (5.26 mm2)	4 AWG (21.15 mm2)
Up to 7 m (23 ft.)	8 AWG (8.37 mm2)	2 AWG (33.63 mm2)
Up to 11 m (36 ft.)	6 AWG (13.30 mm2)	0 (1/0) AWG (53.48 mm2)

Grounding the Sonar Module
The ground post is located to the right of the power supply connector.
Connect the ground post to the boat water ground circuit.
NOTE: The boat battery ground is an acceptable alternative if your vessel does not have a designated water ground circuit.

Networking Considerations
This device uses Garmin BlueNet networking technology and is compatible with both Garmin BlueNet devices and legacy Garmin Marine Network devices. For more information about Garmin BlueNet technology, including best practices for constructing a network including both Garmin BlueNet devices and legacy Garmin Marine Network devices, go to garmin.com/manuals/bluenet.
Before connecting this device to the network, observe the following considerations:

If your boat is equipped with a Garmin BlueNet chartplotter such as a GPSMAP® 9000 series chartplotter, you should use the included Garmin BlueNet cable to connect the GSD 28 device to an open network port or to a Garmin BlueNet 20 switch.
If your boat is equipped with a Garmin BlueNet chartplotter and uses a Garmin BlueNet 30 gateway to connect legacy Garmin Marine Network devices, you can either connect the GSD 28 device to a Garmin BlueNet device using the included Garmin BlueNet cable, or you can connect the GSD 28 device to a legacy Garmin Marine Network device using the included adapter cable. Routing the sonar module through the legacy side of your marine network does not impact its performance.
If your boat is equipped with only legacy Garmin Marine Network devices, you must use the included adapter cable to connect the GSD 28 device to your network.

Manually Configuring a Transducer
Before you can manually configure a transducer, you must connect it to the sonar module using a wiring method that allows for manual configuration (Connecting a Transducer for Manual Configuration,).

On a chartplotter connected to the same network as the sonar module, from a sonar view, select Options > Sonar Setup > Installation > Transducers.
Select the GSD 28 sonar module.
Select Manual Configuration.
If more than one transducer is connected to the sonar module, select an option:
- To configure the transducer connected to the terminals labeled LOW, select Low.
- To configure the transducer connected to the terminals labeled HIGH, select High.
Select Manual Enabled to turn on manual configuration.
Set the parameters for your transducer.
Select Done.

Manual Transducer Configuration Parameters
NOTICE
If parameters are set incorrectly, manual transducer configuration may damage your transducer. If necessary, you should contact your transducer’s manufacturer to verify the correct configuration parameters.

Impedance: The transducer’s minimum impedance, in ohms.
Max. Transmit Power: The transducer’s maximum transmit power, in watts.
Nominal Freq.: The transducer’s nominal frequency, in kHz. If your transducer doesn’t have a nominal frequency, set it to any frequency within its range. This will automatically set a frequency preset for this transducer.
CHIRP: Turn on if configuring a CHIRP transducer.
Lower 3dB Freq.: The lower frequency limit of CHIRP sweeps, in kHz.
Upper 3dB Freq.: The upper-frequency limit of CHIRP sweeps, in kHz.

Transducer Wiring Diagrams
You can use these diagrams to identify the connection points for your transducer wires on the GSD 28 terminal block. Locate your transducer model in the wire color tables (Transducer Wire Color Tables,) for more information.
NOTE: For better visibility, the wiring block label is duplicated in the diagrams below. The GSD 28 device has one terminal block label, placed in front of the terminal block.
Single-Element Transducers
You can connect a single-element transducer to the terminals labeled LOW or HIGH, regardless of nominal frequency. To ensure proper transducer identification and safe operation, you must connect each single-element transducer to its own set of terminals.

Dual-Element Transducers
NOTICE
Connecting the high-frequency wires to the low-frequency terminal block, or the low-frequency wires to the high-frequency terminal block, damages the device and the transducer.
For dual-element transducers, the low-frequency element wires must be connected to the terminals labeled LOW and the high-frequency element wires must be connected to the terminals labeled HIGH. Ground (GRND), temperature (TEMP), XID and GID wires can be connected to either set of terminals.

Two Single-Element Transducers
To ensure proper transducer identification and safe operation, you must connect each single-element transducer to its own set of terminals.

Transducer Wire Color Tables

Single-Element Transducers
You can connect a single-element transducer to the terminals labeled LOW or HIGH, regardless of nominal frequency. To ensure proper transducer identification and safe operation, you must connect each single-element transducer to its own set of terminals.

Transducer Model|

+

|

SHIELD

|

−

|

GRND

|

SHIELD

|

TEMP

|

XID

|

GID1

|

GID2

| Ground Post
---|---|---|---|---|---|---|---|---|---|---
Garmin GT12M- THF| Red| N/A| Black| Bare| N/A| White| N/A| Yellow| N/A| N/A
Garmin GT15M- THF| Red| N/A| Black| Bare| N/A| White| N/A| Yellow| N/A| N/A
Airmar TM185M| Blue| Bare| Black| Brown| N/A| White| Orange| N/A| N/A| Bare
Airmar B175L| Blue/ White| Bare| Black/ White| Brown| N/A| White| Orange| N/A| N/A| Bare
Airmar B175M| Blue| Bare| Black| Brown| N/A| White| Orange| N/A| N/A| Bare
Airmar B175H| Blue| Bare| Black| Brown| N/A| White| Orange| N/A| N/A| Bare
Airmar TM150M| Blue| N/A| Black| Brown| N/A| White| Orange| N/A| N/A| Bare
Airmar B150M| Blue| N/A| Black| Brown| N/A| White| Orange| N/A| N/A| Bare
Airmar B75L| Blue/ White| Bare| Black/ White| Brown| N/A| White| Orange| N/A| N/A| Bare
Airmar B75M| Blue| Bare| Black| Brown| N/A| White| Orange| N/A| N/A| Bare
Airmar B75H| Blue| Bare| Black| Brown| N/A| White| Orange| N/A| N/A| Bare

Dual-Element Transducers
Dual-element transducer wires must be connected to the specified terminals.

Transducer Model

|

LOW +

| LOW SHIELD|

LOW −

|

GRND

|

SHIELD

|

TEMP

|

XID

|

GID1

|

GID2

|

HIGH +

| HIGH SHIELD|

HIGH −

| Ground Post
---|---|---|---|---|---|---|---|---|---|---|---|---|---

Airmar 509LHW

| Blue/ White1|

Bare

| Black/ White|

Brown

|

Bare

|

White

|

Orange

|

N/A

|

N/A

|

Blue

|

Bare

|

Black

|

Bare

Airmar R509LH

| Blue/ White1|

Bare

| Black/ White|

Brown

|

Bare

|

White

|

Orange

|

N/A

|

N/A

|

Blue

|

Bare

|

Black

|

Bare

Airmar CM599LHW|

Blue/White

|

Bare

| Black/ White|

Brown

|

Bare

|

White

|

Orange

|

N/A

|

N/A

|

Blue

|

Bare

|

Black

|

Bare

Airmar CM599LH

|

Blue/White

|

Bare

| Black/ White|

Brown

|

Bare

|

White

|

Orange

|

N/A

|

N/A

|

Blue

|

Bare

|

Black

|

Bare

Airmar R599LH

| Blue/ White1|

Bare

| Black/ White|

Brown

|

Bare

|

White

|

Orange

|

N/A

|

N/A

|

Blue

|

Bare

|

Black

|

Bare

Airmar R109LHW

| Blue/ White1|

Bare

| Black/ White|

Brown

|

Bare

|

White

|

Orange

|

N/A

|

N/A

|

Blue

|

Bare

|

Black

|

Bare

Airmar R109LM

| Blue/ White1|

Bare

| Black/ White|

Brown

|

Bare

|

White

|

Orange

|

N/A

|

N/A

|

Blue

|

Bare

|

Black

|

Bare

Airmar R109LH

| Blue/ White1|

Bare

| Black/ White|

Brown

|

Bare

|

White

|

Orange

|

N/A

|

N/A

|

Blue

|

Bare

|

Black

|

Bare

Airmar R111LH

| Blue/ White1|

Bare

| Black/ White|

Brown

|

Bare

|

White

|

Orange

|

N/A

|

N/A

|

Blue

|

Bare

|

Black

|

Bare

Airmar M265LH

| Blue/ White1|

Bare

| Black/ White|

Brown

|

N/A

|

White

|

Orange

|

N/A

|

N/A

|

Blue

|

Bare

|

Black

|

Bare

Airmar B265LM

| Blue/ White1|

Bare

| Black/ White|

Brown

|

N/A

|

White

|

Orange

|

N/A

|

N/A

|

Blue

|

Bare

|

Black

|

Bare

Airmar B265LH

| Blue/ White1|

Bare

| Black/ White|

Brown

|

N/A

|

White

|

Orange

|

N/A

|

N/A

|

Blue

|

Bare

|

Black

|

Bare

Airmar TM265LM

| Blue/ White1|

Bare

| Black/ White|

Brown

|

N/A

|

White

|

Orange

|

N/A

|

N/A

|

Blue

|

Bare

|

Black

|

Bare

Airmar TM265LH

| Blue/ White1|

Bare

| Black/ White|

Brown

|

N/A

|

White

|

Orange

|

N/A

|

N/A

|

Blue

|

Bare

|

Black

|

Bare

Airmar PM265LM

|

Blue/White

|

Bare

| Black/ White|

Brown

|

N/A

|

White

|

Orange

|

N/A

|

N/A

|

Blue

|

Bare

|

Black

|

Bare

Airmar PM265LH

|

Blue/White

|

Bare

| Black/ White|

Brown

|

N/A

|

White

|

Orange

|

N/A

|

N/A

|

Blue

|

Bare

|

Black

|

Bare

Airmar B275LHW

|

Blue/White

|

Bare

| Black/ White|

Brown

|

N/A

|

White

|

Orange

|

N/A

|

N/A

|

Blue

|

Bare

|

Black

|

Bare

Airmar PM411LWM|

Blue/White

|

Bare

| Black/ White|

Brown

|

N/A

|

White

|

Orange

|

N/A

|

N/A

|

Blue

|

Bare

|

Black

|

Bare

Yellow before 11/20/10

Status LED
After the sonar module is installed, it turns on when the chartplotter is turned on. The status LED on the sonar module indicates its operational status.

LED Color	State	Status
Red	Solid	The sonar module is booting.
Green	Flashing	The sonar module is connected to a chart plotter and is

operating properly.
Red| Flashing| The sonar module is turned on but is not connected to a chart plotter, or is waiting to connect to a chartplotter.
Orange| Flashing| A software update is in progress.
Red/Green| Flashing| The sonar module is in test mode.
Red/Orange| Flashing| The sonar module terminal block lid is open.
Red| Flashes twice followed by a 3- 3-second pause| Other sonar failure. Check all connections.
Red| Flashes three times followed by a 3-second pause| The transducer is not detected by the sonar module.
Red| Flashes four times followed by a 3-second pause| The sonar module input voltage is below the minimum required input voltage.
Red| Flashes five times followed by a 3-second pause| The sonar module input voltage is above the maximum allowed input voltage.

Specifications

Size L x W x H: 270.65 x 366.55 x 101 mm (10.66 x 14.43 x 3.98 in.)

The device withstands incidental exposure to water of up to 1 m for up to 30 min. For more information, go to www.garmin.com/waterrating
Dependent on transducer rating and depth.
Maximum depth is dependent on the transducer, water salinity, bottom type, and other water conditions.

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Garmin® and the Garmin logo are trademarks of Garmin Ltd. or its subsidiaries, registered in the USA and other countries. GSD and Garmin BlueNet™ are trademarks of Garmin Ltd. or its subsidiaries. These trademarks may not be used without the express permission of Garmin.
Airmar™ is a trademark of Airmar Technology Corporation. © 2023 Garmin Ltd. or its subsidiaries support.garmin.com