Hello, I have Furuno 628. When the device starts up, the first screen appears, it locks up and then shuts down after a certain period of time. thank you
Check the battery voltage on the boat, ensure you have a minimum of 11.5 volts and that it is not dropping down. If the voltage drops below approx. 11 volts the unit will shut down due to low voltage to protect the power supply.
If you've checked the power supply on the ship and it's constantly 12 - 14vdc, and doesn't drop than I would recommend sending it in for a repair evaluation at the Camas, WA. service repair center. There may be some diagnostics that can be performed at the repair center to determine the cause of the issue.