GNX™ 21: Navigation Instrument

The display dimensions of the Garmin GNX 21 are as follows:

Without sun cover (H×W×D): 110 x 115 x 30 mm (4.33 x 4.53 x 1.18 in.)With sun cover (H×W×D): 115 x 120 x 35.5 mm (4.53 x 4.72 x 1.40 in.)

The weight of the Garmin GNX 21 display is:

Without sunshade: 247 g (8.71 oz.)With sunshade: 283 g (9.98 oz.)

The GNX 21 display can show a wide range of marine data from compatible sensors and devices via the NMEA 2000 network. This includes, but is not limited to:

System timeRudder angleShip headingEngine parameters (fast and dynamic updates)Battery statusSpeed through waterDepth of waterGNSS position data (fast updates, COG and SOG)Navigation warningsWind dataEnvironmental parameters (including temperature)

The GNX 21 offers several predefined display profiles to suit different types of sailing:

POWERBOAT: Displays instruments useful for powerboat navigation, such as GPS speed, GPS heading, depth, bearing to waypoint, distance to next waypoint, and water temperature.

CRUISING SAILBOAT: Designed for cruising sailboats, it displays true wind speed, GPS speed, GPS heading, bearing to waypoint, distance to next waypoint, true wind angle, and depth.

RACING SAILBOAT: Optimized for racing, this profile includes GPS speed, true wind speed, true wind angle, heading, bearing to waypoint, and distance to next waypoint.

CUSTOM: Allows you to configure the display to your specific needs, with a default page showing ground speed information.

The Garmin GNX 21 display housing is made of fully waterproof polycarbonate, while the lens is glass with an anti-reflective finish for improved visibility.

Yes, the GNX 21 display allows you to customize the data fields shown. You can configure the instrument pages to display the most relevant information for your sailing needs. The 'CUSTOM' profile is specifically designed for this purpose, letting you select from a wide range of data such as speed, heading, depth, wind data, GPS position, and more.

The regatta timer function on the GNX 21 is a dedicated tool for sailboat racing. It allows precise tracking of race time. To quickly access this screen, hold down the ≡ button from any main page.

When choosing the mounting location for the GNX 21, the following points must be considered:

The location must be at eye level or below for optimal visibility while using the vessel.The viewing angle must be less than 50° for the GNX 21 (screen color inversion occurs beyond 60° in the 1 o'clock direction).The mounting surface must be strong enough to support the device's weight and protect it from excessive vibration or shock.To avoid interference with a magnetic compass, the device must not be installed closer to a compass than the specified safety distance of 209 mm (8.25 in.).The space behind the mounting surface must allow for cable routing and connections.

To install the GNX 21 display in a flush mount, follow these steps:

Cut out the flush mount template (included) and ensure it fits the chosen location.Remove the adhesive protection from the template and attach it to the mounting location.Use a 90 mm (3.5 in.) hole saw or rotary tool to cut the mounting surface along the dotted line of the template.Drill pilot holes of 2.8 mm (7/64 in.) for the mounting screws.Apply the included sealant to the back of the unit and marine sealant around the seal.Connect all necessary cables to the unit before placing it into the cutout.Insert the display into the cutout and secure it firmly with the provided screws.Snap the bezel into place.It is recommended to use the template provided in the product box for cutting.

The GNX 21 display connects to a NMEA 2000 network on your boat. This network provides power to the instrument and data from NMEA 2000 devices, such as a wind sensor. The included NMEA 2000 cables and connectors allow you to connect the device to an existing NMEA 2000 network or to create a basic network if needed. A NMEA 2000 power cable, one or more T-connectors, a drop cable, and terminators are typically required for a proper installation.

When connecting the NMEA 2000 power cable, the following precautions must be taken:

Only one NMEA 2000 power cable is required for the network to function properly.A NMEA 2000 power isolator (010-11580-00) must be used if the manufacturer of the existing NMEA 2000 network is unknown.The NMEA 2000 power cable must be connected to the boat's ignition switch or another inline switch. NMEA 2000 devices can drain your battery if the power cable is directly connected to it.

The safe distance from a magnetic compass for the Garmin GNX 21 display is 209 mm (8.25 in.). It is critical to respect this distance to avoid interference with the compass operation.

Yes, the Garmin GNX 21 display is natively compatible with NMEA 2000 networks. It is designed to integrate easily into an existing NMEA 2000 network or to create one, enabling the reception and display of data from multiple sensors and compatible devices.

Yes, the GNX 21 display can receive NMEA 0183 data from a compatible device using an NMEA data cable (not included). However, it cannot transmit this NMEA 0183 data to the NMEA 2000 network.

Yes, the GNX 21 display can receive data from Nexus instruments and sensors using a GND™ 10 device (sold separately). The GND 10 acts as a bridge between Nexus instruments and the NMEA 2000 network.

The Garmin GNX 21 display has an IEC 60529 IPX7 waterproof rating. This means the unit can withstand accidental immersion in water up to 1 meter deep for a maximum of 30 minutes.

The Garmin GNX 21 display is designed to operate within a temperature range of -15°C to 70°C (5°F to 158°F). It is critical to keep the unit within this range to prevent damage from extreme temperatures.