I would first suspect the boat power (amperage) is dropping to the point the radar doesn't have enough power to operate so the unit shuts down to protect itself. If that isn't it it could be the power board in the display has an issue and overheats at some point and shuts down. If it was the motor start up circuits or the modulator board it would always shut off the instance you go to transmit. I think the largest percentage falls on the boat power system.