Furuno GP-3500F - Manual (Page 152)

9. CUSTOMIZING YOUR UNIT
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9.8.2 Removing the password
To remove the password, do the following:
1. Press the [MENU] key to show the main menu.
2. Press the [0] key to show the SYSTEM SETUP menu.
3. Press the [6] key to show the TEST & MEMORY CLEAR menu.
4. Press the [7] key to select RESET PASSWORD.
5. Press the [ENTER] knob to remove the password, or the [CLEAR] key to
escape.
6. Press the [MENU] key several times to close the menu.