Garmin GPSMAP 421 Chartplotters
Garmin Garmin 421S
  • Garmin GPSMAP 421 Chartplotters

Garmin GPSMAP 421, 421S Chartplotters

The Garmin GPSMAP 421 and 421S Chartplotters feature an ultra-bright 4" QVGA color display, a built-in, satellite-enhanced worldwide basemap, and a high-speed digital design that increases map drawing and panning speeds.

Both models have an SD card slot that makes it easy to add additional maps without a computer connection. BlueChart g2 Vision Cards can be added for improved features and functionality including high-resolution satellite imagery and Auto Guidance technology. In addition, MarinerEye view and FishEye view provide a clear 3-D perspective of map information both above and below the water.

The sounder version, GPSMAP 421s, also comes with a powerful dual frequency transducer that clearly paints depth contours, fish targets, and structures.

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Tech Spec Product Info User Generated Content

Garmin's GPSMAP 421 and 421s are NMEA 2000-certified for easy connectivity with sensors, instruments and future marine offerings. The GPSMAP 421 can also receive U.S. graphical weather data via an optional GXM 51 satellite receiver/antenna.

  • GMN-0100076400 -- GPSMAP 421 chartplotter
  • GMN-0100076401 -- GPSMAP 421S chartplotter/fishfinder sounder version includes a dual frequency transom/trolling mount transducer
  • GMN-0100076402 -- GPSMAP 421S chartplotter/fishfinder sounder version without transducer. Choose a transducer to match your application (sold separately)
401 Chartplotter Series Comparison  GPSMAP 421/421S  GPSMAP 431/431S  GPSMAP 441/441S 
Unit dimensions (W x H x D):  5.7" x 5.0" x 2.7"  5.7" x 5.0" x 2.7"  5.7" x 5.0" x 2.7" 
Display size (W x H):  2.4" x 3.2" (4.0" diagonal)  2.4" x 3.2" (4.0" diagonal)  2.4" x 3.2", 4.0 (4.0" diagonal) 
Display resolution (W x H):  240 x 320 pixels   240 x 320 pixels   240 x 320 pixels  
Display type:  QVGA display   QVGA display   QVGA display  
Weight:  1.3 lb (590 g)   1.3 lb (590 g)   1.3 lb (590 g)  
Battery: 
Battery life: 
Waterproof:  Yes (IPX7)   Yes (IPX7)   Yes (IPX7)  
High-sensitivity receiver:  Yes  Yes  Yes 
Antenna:  Internal   Internal   Internal  
NMEA input/output:  NMEA 0183 Compatible; NMEA 2000 Certified  NMEA 0183 Compatible  NMEA 0183 Compatible; NMEA 2000 Certified 
Basemap:  Yes  Yes  Yes 
Preloaded street maps:  Yes (Inland Maps)  Yes (Coastal Maps) 
Ability to add maps:  Yes  Yes  Yes 
Built-in memory:  None (Cannot Load Maps to Internal Memory)  None (Cannot Load Maps to Internal Memory)  None (Cannot Load Maps to Internal Memory) 
Accepts data cards:  SD Card Slot  SD Card Slot  SD Card Slot 
Waypoints/favorites/locations:  3,000   3,000   3,000  
Routes:  100  100  100 
Track log:  10,000 points; 50 saved tracks   10,000 points; 50 saved tracks   10,000 points; 50 saved tracks  
Garmin radar compatible: 
Garmin sonar compatible:  Yes  Yes  Yes 
CANet compatible: 
Garmin Marine Network compatible: 
Supports AIS (tracks target ships' position):  Yes  Yes  Yes 
Touchscreen: 
Supports DSC (displays position data from DSC capable VHF radio):  Yes  Yes  Yes 
Audible alarms:  Yes  Yes  Yes 
Tide tables:  Yes  Yes  Yes 
Hunt/fish calendar: 
Sun and moon information:  Yes  Yes  Yes 
3-D map view:  Yes (With Optional BlueChart g2 Vision Card)   Yes (With Optional BlueChart g2 Vision Card)   Yes (With Optional BlueChart g2 Vision Card)  
Auto Guidance:  Yes (With Optional BlueChart g2 Vision Card)   Yes (With Optional BlueChart g2 Vision Card)   Yes (With Optional BlueChart g2 Vision Card)  
Automatic routing (turn by turn routing on roads): 
XM WX Weather & Radio for U.S. & Canada compatible:  Yes  Yes 
Voice prompts (e.g. "Turn right in 500 ft."): 
Speaks street names (e.g. "Turn right ON ELM STREET in 500 ft."): 
Remote control: 
Headphone jack/audio line-out: 
Audio/video input/output: 
Portable: 
Automotive/motorcycle-friendly: 
BRAND: Garmin
Type: GPS Chartplotter
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