Where is graph picking up interference

[rickhise]

When trolling motor is set to #3 on the power level 1 through 10 being options graph show screen interference. The desired power level for bottom watching with a live bait drift, depth near 25 feet.


Trolling motor minn Kota Trevor foot control is on its own battery by its self
graph gets its power off power off fused power strip.
no pumps are anything is on
sensitifity on graph doesn't make a difference. Till it's turned completely off then I can't get a structure read but do get the bottom read without interference

cord to trolling motor cord not near any part of graph wire ing. It's like the distortion is a result of the spin of the prop on the TM. Had this combination for years I guide so it's used daily

any thoughts

 

[johnnygjr]

the interference is caused by a/c voltage created by electric trolling motor.I think a condenser can be installed where 12volt connection is.

 

[papyson]

both of these are swags but first I would check and make sure all battery connections are good...2nd I would not overlopk the possibility of water in the trolling motor or a bad connection in it..

is this a metal boat?