Raymarine C-70 DSM300 goes offline

[drichitt]

The depth sounder part of my C-70 system, the DSM300, will generally disengage within 10-15 after the motor is turned off. It happens sooner if much else is operating (i.e. live well pump). Seems to be insufficient voltage. By insufficient, I think the disconnect happens at and below 12 volts. I have had my batteries tested and been assured they are ok, but I have my doubts. They are plenty strong to start the engine, but should they hold their voltage levels better than 12 volts. Thanks...Don