GMR™ 21

Part Number: 010-00323-01


The 24-inch GMR 21 digital radar and its more powerful counterpart, the GMR 41, help you steer clear of hazards, giving you more confidence and peace of mind on the water.

Track Targets

The GMR 21 packs 2 kilowatts of transmit power and a range of 24 nautical miles. With 3.6° horizontal beamwidth, the GMR 21 offers clear target definition in all weather conditions. The GMR 21 processes raw data within the radome for fast and efficient presentation of radar signatures.

You can also use the GMR 21 to avoid traffic on the water with MARPA target tracking, which allows you to track the bearing, course, speed and predicted closest approach of up to 10 targets.

Easily Connect to the Garmin Marine Network

The GMR 21 transmits data over the Garmin Marine Network, a 100-megabit plug-and-play proprietary network that gives you the ability to expand your boat’s system as needed. Once connected to the network, any network-compatible Garmin chartplotter can double as your radar screen. And as an aid to locational awareness, you can overlay the GMR 21 radar image on the chartplotter's map page. You can also split the on-screen display so that you can view the map and the standard radar page simultaneously.

Marine Network


PDF Download detailed specs

Physical & Performance

Physical dimensions 24" diameter, 8" high (71.1 cm diameter, 20.3 cm high)
Weight 26 lb (11.8 kg)
Water rating IPX7
Power consumption 25 W typical
Rotation speed (RPM) 24 rpm
Transmit power 2 kW
Power input 10-35 V DC
Beam width 3.6° horizontal, 25° vertical
Maximum range 24 nm
Minimum range 35 meters
Radar type Radome

Radar Features

MARPA target tracking (collision avoidance) Yes (Requires Heading Sensor, Sold Separately)
Guard zone alarm
Color 2 bit

In the Box

  • GMR 21
  • Mounting hardware kit
  • Power/netework cable
  • Cable grommet
  • Owner's manual
  • Installation instructions


Compatible Devices