Humminbird 300 SERIES 345C DI - Manual (Page 44)

Start-Up Options Menu
Press the MENU key during the power on sequence to view the Start-Up
Options Menu, and select one of the modes described on the following pages.
Also, see Power On for additional information.
Normal
Use Normal for on-the-water operation with a transducer connected. If a
functioning transducer is connected, Normal operation will be selected
automatically at power up, and your Fishfinder can be used on the water.
To exit Normal operation, power off your Fishfinder.
Start-Up Options Menu 35