OK......so I've got a pretty little 7 series hummingbird on the back and a 5 series on the front.

24v trolling system on separate batteries.
12v cranking battery that is also configured to run all accessories. Lights bilge, finders, etc, etc.

The front finder has a transducer on the trolling motor. It works flawlessly, no noise, no issues...works great.

The back finder has noise problems whenever you hit the trolling motor.......I've tried everything, including the following:

1). Ran separate wires on opposite side of the boat to the battery from the finder. NO go. Still noise.
2). Put noise chokes on those wires.........Still noise.
3). Put noise chokes on the trolling motor power wires..........Still noise.
4). Put noise chokes on all the power wires above AND on the Transducer.....Still noise.
5). Temp soldered a ground wire to the trolling motor housing, and then ran this to the negative post of the battery.....Still NOISE.

The ONLY thing that eliminated the noise was to grab a separate battery, outside of the boat, and hook the fish finder to that. That worked, but I don't have room in the boat for another battery. This is really honking me off.

Does anyone have an idea that I can try to help resolve the noise problems.

I don't get noise while running the main outboard........only when running the Trolling Motor. I'm assuming I have a ground loop issue, but I'm at my end trying to resolve it.

Later,

Geo