Locked up screens, erroneous depth readings and vertical hash marks on the screen are symptoms of electrical interference. Electric trolling motors or several sonars operating in close proximity are frequent causes of the problem. Reduce the problem by connecting only the trolling motor to the trolling motor batteries. Ground the trolling motor battery. Connect all electronics to the starting battery or a separate battery. Vary sounding or ping rates on the sonar if possible.
Bill Diedrich is a retired Minnetonka math teacher with a love of fishing electronics.
