Furuno GP-1610CF Operator's Manual page 23

If the bottom is displayed in red and the light-blue color appears
the mounting location is suitable. You can leave the transducer
in position.
If the bottom is not displayed in reddish brown, the mounting
location is unsuitable. Relocate the transducer and do the
following.
1. Press the POWER key to turn off the power.
2. Gently dismount the transducer with piece of wood.
3. Do steps 1 through 5 in the previous procedure. Repeat until
a suitable location is found.
Final preparation
Support the transducer with a piece of wood to keep it in place
wile it is drying. Let the transducer dry 24–72 hours.
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