I was using a HB 588ci with my Minn Kota Terrova US2 transducer and it worked very well. I replaced the 588ci with a Helix 7 2D/GPS and now I have a lot of interference on the sonar screen. It is definitely from the TM, when it's running the screen is "snowy", when it's not running, the screen is perfect. What can I do?