This topic's probably been touched on 14,000 times so let me say i'm sorry right up front. I just bought and installed a humminbird 678c on thw bow of my boat and I've got a powerdrive with us2. I carried it out wednesday and my depth stayed at 6 feet all day. Also, my graph just shows a yellow screen and never shows any change of bottom contour or structure. The water temp seems to be the only thing working. I wired the power through the trim switch on on the front of my boat so i know it's running off a 12v source. Does this sound like an interference issue? Could the transducer in my trolling motor be shot? If anyone has any advice please chime in. Also, if anyone has a pic of what interference looks like maybe you could post them or direct me to somewhere that i can find them. Im pretty much electronically illiterate so if you do respond to this im sure i'll have more questions. Thanks in advance for y'alls help