CORRECT CRAFT Nautique 220 Owner's Manual page 98

Speedometer Function
The speedometer measures speed over the water using a paddle
wheel sensor.
Speedometer Calibration
The analog speedometer displays the speed of the boat through the
water. The speedometer is calibrated at the factory however,
significant variations can occur due to changes in installations. The
speedometer can be easily calibrated to a known reference such as
a radar gun, measured course, or GPS.
When the unit is in digital speed display mode, push and release M
to put the speedometer in the calibration mode. Push and hold M
down for at least two seconds, the LCD will show "AdJUST."
Run the boat at a constant 30 MPH as measured by the GPS, radar,
or closed course. Adjust the speedometer pointer by pressing L
and M until the speedometer matches the known speed.
When finished, press M to exit the adjustment screen. The operator
has the option of saving or canceling the adjustment procedure.
The options can be selected using L and M. To save the calibration
setting, press and hold M for two seconds when the display shows
"SAVE."
Controls and Indicators
Calibration Display
Save Display
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