Quote Originally Posted by justinp61 View Post
IMO, issues in aluminum boats arise when the boat is used as a ground. Unless there is something I haven't seen, (and that is a distinct possibility) there is no way to install an outboard with electric start/charging system on an aluminum boat without having continuity between the battery negative and the boat hull. Again, IMO the key is not using the hull as a ground path to the battery.

My Fortrex had the internal ground with a fuse. The fuse never blew, and I never got rid of interference no matter where the wires were run or how many chokes were on the wires. How the noise from the 24v TM found its way to 12v system, I can only guess. My guess is that the trolling motor ground also had continuity to the hull and when the TM was running the 12v system picked up the noise. The brushless TM fixed it.
On a PWM motor, radio frequency noise is radiated through the air. Pretty strong signal and very broad band. Couples into wiring and directly into electronics.