Quote Originally Posted by Dutch View Post
I had that issue years ago with my old MK Powerdrive 2 and a HB 575 DI unit... it took several ferrite cores to fix the problem. My HB 999SI came with a pre installed choke on the power cord. My Garmin has something similar.

Some good info on the subject here...

RF Interference in Trolling Motors - AAARGH! Sonar Noise! by Adam Broughton
I have tried all this in thir article and many fixes on Youtube but nothing has fixed it yet. It seems to be an issue with Garmin and quite common. I am going to try this fix and if this fails, the Garmin is gone.

YouTube