Have had this issue for a while now, used to have my bow sonar powered by the trolling batteries, I figured that was causing the problem.

This week I changed the wiring over and have it powered by the starting battery, but the problem still persists.

When I start the trolling motor, the sonar gets a sort of white noise effect for a second.

Anything I can do to fix this? I've read something about a ferrite core?

The sonar is a Garmin Striker 5DV, the motor is a Terrova 80. I'm using the Garmin transducer, mounted to the TM.