I have tried everything.
Running off cranking battery
Trolling motor wire on oneside of boat, electronics on other
grounded TM housing to TM battery negative.
Chokes for the Transducer cable and the power cable
Nothing worked.
I had a second boat pulled up beside mine, I plugged it's power source into my 597CIDI and left the sonar cable plugged in on my boat. I also moved the transducer away from the trolling motor and put the noise cancellation on high 1. it got rid of the problem. the closer I moved the transducer to the trolling motor, it gradually got worse. You have to be about a 1.5ft from the TM in order to get rid of the interference. Once I plugged the unit into the power source on my boat, it got increasingly worse.
Here is something for you, I plugged in my 898SI into the power supply and the transducer for the 597 that was giving me problems and I did not see the interference on the 898SI.
I'm not sure what is going on but this is unacceptable.