Bought a new 858c for the front and a 958 series DI and SI for the back. When using the terrova i begin to get lines in the screen, when i shut it off the graph works fine?? some how ther is interference, just clueless wher to look or if ther is a setting to play with. With the rear one, when i start the big motor and begin to power up is also begins to have lines showing up. Also after about 10mph is wont read depth. Running a 2025 prov and suggestions?? thanks

Try powering them with an isolated temporary battery, even if it's out of a lawnmower. That will isolate the issue if it works.

Get a filtered power cord from Humminbird. I had the same issue and this solved the problem.

Same issue with my 998SI. When Terrova is running side imaging usually has faint horizontal lines very close together. Turn off the Terrova and clear as a bell....I just ordered the cable. I think the part number is PC11.