garmin 240 high voltage warning

[Stainless]

I had my boat out this past weekend for the first time this year an I had an unusual warning with my fish finders. Both the bow and dash mount finders are garmin 240's and would beep after 5 seconds of powering them up and give a "high voltage warning" message then shut themselves off. I tried turning them on numerous times but it never failed to happen. The only time they worked properly was at wide open or close to wide open throttle. Any suggestions as to what might be causing this?

[Valv]

Might be your voltage regulator/alternator/rectifier on motor is bad and is putting out too much charge.

Have it checked to save life of batteries, instruments, etc.

[fishermn]

Val is correct, I would get this fixed ASAP or you will eventually cook your battery as well.

[mnrstrider]

Check the water level in your batteries too, make sure they are ok.