Garmin GNX 120, GMI 20, GND 10 Installation Instructions

GMI™ 20 Installation Instructions

To obtain the best possible performance, install this marine
instrument according to these instructions. If you experience
difficulty during the installation, contact Garmin® Product
Support, or seek the advice of a professional installer.

This instrument communicates with NMEA 2000® sensors and
devices, and shows information such as speed, heading, water
depth, and fuel information when connected to the appropriate
sensors. The instrument can also communicate with a NMEA
0183 device using an optional data cable.

Important Safety Information

WARNING

See the Important Safety and Product Information guide in the
product box for product warnings and other important
information.

CAUTION

Always wear safety goggles, ear protection, and a dust mask
when drilling, cutting, or sanding.

NOTICE

When drilling or cutting, always check what is on the opposite
side of the surface.

Registering Your Device

Help us better support you by completing our online registration
today.

• Go to http://my.garmin.com.

• Keep the original sales receipt, or a photocopy, in a safe
place.

Contacting Garmin Product Support

• Go to www.garmin.com/support and click Contact Support
for in-country support information.

• In the USA, call [phone] or [phone].

• In the UK, call 0808 2380000.

• In Europe, call +44 (0) 870.8501241.

Mounting Considerations

NOTICE

This device should be mounted in a location that is not exposed
to extreme temperatures or conditions. The temperature range
for this device is listed in the product specifications. Extended
exposure to temperatures exceeding the specified temperature
range, in storage or operating conditions, may cause device
failure. Extreme-temperature-induced damage and related
consequences are not covered by the warranty.

Using the included hardware and template, you can flush mount
the device in the dashboard. If you want to mount the device
using an alternative method where it appears flat with the front
of the dashboard, you must purchase a flat-mount kit
(professional installation recommended) from your Garmin
dealer.

When selecting a mounting location, observe these
considerations.

• The mounting location should be at or below eye level to
provide optimal viewing as you operate your vessel.

®

• The mounting location should allow easy access to the keys
on the device.

• The mounting surface must be strong enough to support the
weight of the device and protect it from excessive vibration or
shock.

• To avoid interference with a magnetic compass, the device
should not be installed closer to a compass than the
compass-safe distance value listed in the product
specifications.

• The area behind the mounting surface must allow room for
the routing and connection of the cables.

Mounting the Device

NOTICE

If you are mounting the device in fiberglass, when drilling the
four pilot holes, it is recommended to use a countersink bit to
drill a clearance counterbore through only the top gel-coat layer.
This will help to avoid any cracking in the gel-coat layer when
the screws are tightened.

Stainless-steel screws may bind when screwed into fiberglass
and overtightened. Garmin recommends applying an anti-seize
lubricant to the screws before installing them.

The included template and hardware can be used to flush
mount the device in your dashboard. To mount the device so
the screen is flat with the dashboard, you must purchase a flat­mount kit from your Garmin dealer.

Trim the flush-mount template and ensure it will fit in the

1

location where you plan to mount the marine instrument.
The flush-mount template is included in the product box.
Remove the liner from the adhesive on the back of the

2

template and apply it to the location where you plan to mount
the marine instrument.

If you plan to cut the hole with a jigsaw instead of a 90 mm

3

(3.5 in.) hole saw, use a 10 mm (3/8 in.) drill bit to drill a pilot
hole to begin cutting the mounting surface.

Using the jigsaw or the 90 mm (3.5 in.) hole saw, cut the

4

mounting surface along the inside of the dashed line
indicated on the flush-mount template.

If necessary, use a file and sandpaper to refine the size of

5

the hole.
Place the marine instrument into the cutout to confirm that

6

the mounting holes on the template are in the correct
locations.

If the mounting holes are not correct, mark the correct

7

locations of the mounting holes.
Remove the marine instrument from the cutout.

8

Drill the 3.2 mm (1/8 in.) pilot holes.

9

If you are mounting the marine instrument in fiberglass, use
a countersink bit as advised in the notice.

Remove the remainder of the template.

10

If you will not have access to the back of the device after you

11

mount it, connect all necessary cables to the device before
placing it into the cutout.

NOTE: To prevent corrosion of the metal contacts, cover
unused connectors with the attached weather caps.

Place the marine instrument into the cutout.

12

Securely fasten the marine instrument to the mounting

13

surface using the supplied screws.
If you are mounting the marine instrument in fiberglass, use

a anti-galling lubricant as advised in the notice.
Snap the bezel À into place.

14

April 2013

190-01609-02_0A Printed in Taiwan

Connection Considerations

The marine instrument connects to power and to data sources
through a NMEA 2000 network. In addition, the marine
instrument can connect to a NMEA 0183 data source using a
data cable (not included).

NMEA 2000 Connection Considerations

NOTICE

If you have an existing NMEA 2000 network on your boat, it
should already be connected to power. Do not connect the
included NMEA 2000 power cable to an existing NMEA 2000
network, because only one power source should be connected
to a NMEA 2000 network.

If you are installing the included NMEA 2000 power cable, you
must connect it to the boat ignition switch or through another in­line switch. NMEA 2000 devices will drain your battery if the
NMEA 2000 power cable is connected to the battery directly.

The marine instrument connects to a NMEA 2000 network on
your boat using the port labeled NMEA 2000. The NMEA 2000
network provides power to the marine instrument and data from
NMEA 2000-compatible devices such as a wind sensor. The
included NMEA 2000 cables and connectors allow you to either
connect the device to your existing NMEA 2000 network or
create a basic NMEA 2000 network if needed.

If you are unfamiliar with NMEA 2000, you should read the
“NMEA 2000 Network Fundamentals” chapter of the Technical
Reference for NMEA 2000 Products. To download the
reference, click the “Manuals” link on the product page for your
device at www.garmin.com.

Item Description

À
Á
Â
Ã
Ä
Å
Æ
Ç
È

Wind sensor

Marine instrument

Ignition or in-line switch

NMEA 2000 power cable

NMEA 2000 drop cable

12 Vdc power source

NMEA 2000 terminator or backbone cable

NMEA 2000 T-connector

NMEA 2000 terminator or backbone cable

NMEA 0183 Connection Considerations

• The marine instrument can receive NMEA 0183 data from
one device using a NMEA data cable (not included), but it
cannot transmit data from the NMEA 0183 device to the
NMEA 2000 network.

• If are replacing a legacy Garmin marine instrument that
currently uses a NMEA data cable, you do not need to
purchase a new data cable, but you might need to replace
the quarter-turn locking ring with a threaded locking ring. See
your local Garmin dealer or www.garmin.com for more
information.

• The installation instructions provided with your NMEA 0183
compatible device should contain the information you need
to identify the transmitting (Tx) A (+) and B (-) wires.

• When connecting NMEA 0183 devices with two transmitting
wires, it is not necessary for the NMEA 2000 bus and the
NMEA 0183 device to connect to a common ground.

• When connecting a NMEA 0183 device with only one
transmitting (Tx) wire, the NMEA 2000 bus and the NMEA
0183 device must connect to a common ground.

• For extended runs, you should use at least 0.33 mm
(22 AWG) wire.

• You must solder and seal all connections with heat-shrink
tubing.

Wire Color Wire Function

Red A red wire is present only on some variations of the data

cable, and should not be connected.

Black Accessory (-). This wire is used only when connecting the

marine instrument to a Garmin HVS GPS antenna.

Yellow Accessory (+). This wire is used only when connecting the

marine instrument to a Garmin HVS GPS antenna.

Blue Tx/A (+). This wire is used only when connecting the

marine instrument to a Garmin HVS GPS antenna.

White Tx/B (-). This wire is used only when connecting the

marine instrument to a Garmin HVS GPS antenna.

2

2

Wire Color Wire Function

Brown Rx/A (+)

Green Rx/B (-)

NMEA 0183 Connection Diagrams

This diagram is an example of a connection to a standard
NMEA 0183 device with two Tx wires.

Item Description

Marine instrument with a NMEA data cable (not included)

À

12 Vdc power source

Á

NMEA 0183-compliant device

Â

Item Garmin Wire

Function

N/A N/A Power

Ê

N/A N/A Data ground

Ë

Rx/A (+) Brown Tx/A (+)

Ì

Rx/B (-) Green Tx/B (-)

Í

This diagram is an example of a connection to a standard
NMEA 0183 device with one Tx wire.

Garmin Wire
Color

NMEA 0183 Device
Wire Function

Item Marine Instrument Wire Color Antenna Wire Color

N/A Red

Ê

Black Black

Ë

Yellow Orange

Ì

Blue White

Í

White White/orange

Î

Brown Gray

Ï

Green White/red

Ð

Specifications

Specification Measurement

Dimensions without sun cover
(H×W×D)

Dimensions with sun cover
(H×W×D)

Weight without sun cover 247 g (8.71 oz.)

Weight with sun cover 283 g (9.98 oz.)

Temperature range From 5° to 158°F (from -15° to 70°C)

Compass-safe distance 209 mm (8.25 in.)

Case material Polycarbonate, waterproof to IEC

Power usage 2.5 W max

Unit max. voltage 32 Vdc

NMEA 2000 input voltage 9–16 Vdc

NMEA 2000 load equivalency
number (LEN)

110 x 115 x 30 mm (4.33 x 4.53 x

1.18 in)

115 x 120 x 35.5 mm (4.53 x 4.72 x

1.40 in)

60529 IPX7 standards

6 (300 mA at 9 Vdc)

Item Description

Marine instrument with a NMEA data cable (not included)

À

NMEA 2000 network (must connect to the same ground as the

Á

NMEA data cable)

12 Vdc power source

Â

NMEA 0183-compliant device

Ã

Item Garmin Wire

Function

N/A N/A Power

Ê

N/A N/A Power ground

Ë

Rx/B (-) Green Data ground

Ì

Rx/A (+) Brown Tx

Í

Garmin Wire
Color

NMEA 0183 Device
Wire Function

This diagram is an example of a connection to a Garmin HVS
GPS antenna.

Item Description

Marine instrument with a NMEA data cable (not included)

À

12 Vdc power source

Á

Garmin HVS GPS antenna

Â

NMEA 2000 PGN Information

Type PGN Description

Transmit and receive 059392 ISO acknowledgment

059904 ISO request

060928 ISO address claim

126208 NMEA: Command, request, and

acknowledge group function

126464 Transmit PGN list group function

126996 Product information

Receive 126992 System time

127245 Rudder

127250 Vessel heading

127488 Engine parameters: Rapid update

127489 Engine parameters: Dynamic

127493 Transmission parameters: Dynamic

127498 Engine parameters: Static

127505 Fluid level

127508 Battery status

128259 Speed: Water referenced

128267 Water depth

129025 Position: Rapid update

129026 COG and SOG: Rapid update

129029 GNSS position data

129044 Datum

129283 Cross track error

129284 Navigation data

129285 Navigation route and waypoint info

129539 GNSS dilution of precision (DOP)

129540 GNSS satellites in view

130306 Wind data

130310 Environmental parameters

130311 Environmental parameters

130312 Temperature

3

Type PGN Description

130313 Humidity

130314 Actual pressure

130576 Small craft status

NMEA 0183 Information

When connected to an optional NMEA 0183-compatible device,
the instrument can receive these NMEA 0183 sentences.

Sentence Description

AAN Auto anchor data

BOD Bearing (origin to destination)

BWC Bearing and distance to waypoint

DBT Depth below transducer

DTM Datum being used

DPT Depth

GGA Global positioning system fix data

GLL Geographic position (latitude and longitude)

GRMB GPS data

GRME GPS position error data

GSA GNSS DOP and active satellites

GSV GNSS satellites in view

HDG Heading, deviation, and variation

HDM Heading, magnetic

HDT Heading, true

MDA Meteorological composite

MTW Water temperature

MWD Wind direction and speed

MWV Wind speed and angle

RMB Recommended minimum navigation information

RMC Recommended minimum specific GNSS data

THS Heading sensor data

VHW Water speed and heading

WPL Waypoint location

XTE Cross track error

You can purchase complete information about National Marine
Electronics Association (NMEA) format and sentences from:
NMEA, Seven Riggs Avenue, Severna Park, MD 21146 USA
(www.nmea.org)

Garmin International, Inc.

1200 East 151st Street

Olathe, Kansas 66062, USA

Garmin (Europe) Ltd.

Liberty House, Hounsdown Business Park

Southampton, Hampshire, SO40 9LR UK

Garmin Corporation

No. 68, Zhangshu 2nd Road, Xizhi Dist.

New Taipei City, 221, Taiwan (R.O.C.)

© 2013 Garmin Ltd. or its subsidiaries www.garmin.com/support

Garmin®, the Garmin logo, and GPSMAP® are trademarks of Garmin Ltd. or its subsidiaries, registered in the USA and other countries.
GMI™ is a trademark of Garmin Ltd. or its subsidiaries. These trademarks may not be used without the express permission of Garmin.

NMEA®, NMEA 2000®, and the NMEA 2000 logo are registered trademarks of the National Marine Electronics Association.