#3806, "Trolling motor interference, solved - finally"
Winter time is the one time when I really start to care about precise electronics. For as long as I've owned my boat I've been plagued by trolling motor interference on the bow graph.
For whatever reason, the interference I got was worst at the motherlode lakes. Pedro and Melones especially. You'd get in to deep water, hit the trolling motor and the graph would light up with interference. It was really bad on my Lowrance X-27, like unusable bad.
On my Humminbird 858 it wasn't as bad but enough to make me crazy trying to watch stupid one pounders in 70 feet. I tried running a ground wire between the last negative post on the trolling motor batteries and the ground on the starter. It helped a tiny bit but not really.
I tried moving the wires around to be sure the trolling motor wires didn't run close to the graph wires. Nothing. I tried isolating the transducer on the trolling motor head using rubber pads. Nothing. I tried the noise filtering settings on the unit. Nothing.
What is really interesting about the Humminbird is that when you run the console graph and the bow graph at the same time, the bow graph registers less interference than when you turn sonar to off on the console graph. I think some kind of algorithm is programmed in to the Humminbirds to recognize when 2 signals are present and reduce clutter.
Anyway. Friday was my day off and I spent the better part of 2 hours fishing a 16ga ground wire from the negative on the starter to the head of the trolling motor. Drilled a hole in the skeg and attached the wire with a small stainless self-tapping screw. A few posts online recommended this and I'll be damned if it didn't totally fix the problem.
I get a tiny blip on the graph when I hit the trolling motor but other than that it's perfect. Clean, perfect picture. Happy times.