Just to let BBC'ers know that the vertical line interference on my front Lowrance HDS-12 Gen3 sonar unit that was created when I turned on my 2018 Minn Kota Ultrex 24V 80lb 45inch trolling motor has finally been eliminated!
The fix was connecting a Shielded Cable with 12 AWG wire in it directly to the bow HDS-12 sonar Power wire, running it through the starboard gunnel, and connecting it directly to the 4 AWG wire from the engine cranking battery that is under rear console. Previously, the Power wire was connected to an electronics board inside the bow console cavity.
The work was done by Ryan McComas, of 12-Volt Accessories, a.k.a. "Rig Ryan" on Facebook, who is based out of Peoria, AZ (basically the Phoenix, AZ metro area).
[One unsuccessful fix was that I added a Mix 77 Ferrite Choke ring to each of the following: to the front sonar Power wire, to the trolling motor Power wire, and to the HDI Transducer wire].