I have a Humminbird 858c Hd Di that I've been trying to correct a bad interference concern from my Huminbird 858c HD Di unit when in the sonar mode for some time now. I've got the down image transducer for this unit mounted to the motor assembly of the MinnKota. The symptoms of the interference only occurs when I press the foot pedal energizing the switch no matter what the speed settings is at. As soon as I step off the pedal switch the interference is gone. there has got to be a fix for this concern?