Name:   GoneFishin - Subject:   Boat noise with batteries off... Date:   5/24/2017 5:36:54 PM (updated 5/24/2017 5:45:24 PM)

The onlt thing I can think of is your bilge pump. It is wired to run even with the power off so if water collects and the float rises to that level it pumps out the water. That keeps boats from sinking that are moored in the water. My pump is in the stern at the lowest point. If you can hear it when standing behind the boat then it is probably the pump.

I have 2 batteries and a cutoff switch. It is wired to bypass the cutoff switch.

If it is your pump, it maybe defective if it is recycling without water raising the float.

Just my 2 cents....