So, I installed my HDI yesterday, took it out this morning and got interference, got on Google and the suggested fixes are:
Run a 18ga wire from your negative on your troll battery to your cranking battery(2 amp fuse inline)
Run a ground wire off of your negative from your power to your graph down to can of the tm head.
Put a ferritt choke on the power cable of the graph.
Check the fuse in the head of your troll motor.
Haven't tried any yet but will post back with results.
Side note: what's the best transducer saver for the HDI?