Do you have your unit wired to the starting battery or is it powered from somewhere at the bow?
If it isn't wired to the starting battery start there. If you still have RFI the get a piece of rubber hose just a bit larger that the transducer cable. Cut a slit down the hose and put the hose onto the transducer cable and wrap it with electrical tape. Put aluminum foil around the transducer cable before placing the hose onto the cable.
It's all coming together and we have you covered @ Shut-Up-And-Fish LLC
for all your Humminbird, Minn Kota & Motorguide needs.
We install & educate as well!!! 972 737 8161