FCV 588 Trolling interference help

[Mgfishing]

Old thread being revisited here but I was never able to nut out the problem, I ran the 588 on a completely seperate battery, transducer opposite side to the power cables and wiring, & still got this noise or interference at trolling speed. When the screen clears up in these photos is when the boat is taken out of gear & not moving! Idle revs don't seem to aggravate it just the low range rpm's, could it possibly be turbulent water? I never thought it may be because the disturbance is the bottom half of the screen not the top

 

[Johnny Electron]

Did you power the unit with a completely isolated battery? Definitely electrical noise going on there by the looks of it.

 

[Mgfishing]

Did you power the unit with a completely isolated battery? Definitely electrical noise going on there by the looks of it.

Them photos are not with an isolated battery but I have done so and get the same result. Any ideas ?

 

[Johnny Electron]

If not coming in via power/grounding, then it is noise being picked up by the transducer from sound on the boat OR an internal issue with the sounder. I would recommend sending the unit in for a full checkout so the unit could be eliminated from consideration or fixed.