Garmin GNX 20/21 User Manual

See the Important Safety and Product Information guide in the 

product box for product warnings and other important 

information.

NOTE: Certain functions are available only when the 

appropriate sensors are connected to the device.
The GNX 20 Marine Instrument with Standard LCD or the GNX 

21 Marine Instrument with Inverted LCD allows you to view data 

provided by sensors connected to the device using a NMEA 

2000® or NMEA® 0183 network.

Select to return to the previous menu or to the instrument 
page.
Select to view the menu for an instrument page.

 or 

Select to scroll through instrument pages and menus.
Select to view the display settings.
Select twice to view backlight settings.
Hold to view the power off settings.

You can use the race timer to count down to a race, and then 

measure the duration of the race. You can add the race timer as 

a data field on a page.
TIP: To quickly open the race timer screen, hold 

 from a main 

page.

From a page with the race timer active, select 

 > 

CONFIGURE DATA FIELDS > RACE TIMER SETTINGS.

Select an option:
• When the device is in prerace mode and is stopped or 

running, select RESET, START, or SETUP.

• When the device is in prerace mode and is running, sync 

the timer to the next minute up or the next minute down, 

or select STOP.

• When the device is in race mode and the race timer is 

counting up, sync the timer back to 0:00, or select STOP.

Profiles are collections of instrument pages that can be 

customized. Profiles can be made up of instrument pages that 

display similar data, such as GPS speed information and GPS 

course information.

During the initial setup, you can select a preset profile, or you 

can create a custom profile. You can select a different profile at 

any time.
POWERBOAT: This profile displays instruments useful when in 

a powerboat. Available default instruments include GPS 

speed information, GPS course information, depth, bearing 

to waypoint, distance to the next waypoint, and water 

temperature.

SAIL CRUISE: This profile displays instruments useful when 

cruising in a sailboat. Available default instruments include 

true wind speed, GPS speed information, GPS course 

information, bearing to waypoint, distance to the next 

waypoint, true wind angle, and depth.

SAIL RACE: This profile displays instruments useful when 

racing in a sailboat. Available default instruments include 

GPS speed information, true wind speed, true wind angle, 

heading, bearing to waypoint, and distance to the next 

waypoint.

CUSTOM: This profile allows you to customize the page to 

display instruments useful to your specific boating needs. 

The default page displays speed over ground information.

Select 

 > SETUP > PROFILES.

Select a profile.

You can restore profiles to their factory default settings.

Select 

 > SETUP > PROFILES > RESET DEFAULTS.

Select CURRENT PROFILE or ALL PROFILES.

From the home page, select 

 or  .

You can use auto scroll to automatically cycle through all of the 

instrument pages.

Select 

.

Select SETUP > AUTO SCROLL.

Select how long each instrument page displays.

Data provided on an instrument page can be shown in various 

ways depending upon the instrument page that is displayed.

Select 

 > CONFIGURE DATA FIELDS.

Some instrument pages display graph data. You can configure 

the data that displays on the graphs.

From the instrument page, select 

 > CONFIGURE DATA 

FIELDS > GRAPH SETTINGS.

Select an option:
• To determine how long the graph data displays, select 

GRAPH DURATION.

• To configure the scale of values displayed in the graph, 

select GRAPH SCALE.

NOTE: Instrument page layout can be changed only on pages 

that display more than one instrument.
You can change the layout of instrument pages to display up to 

three instruments from any category.

Introduction

1