humminbird interference

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Been there, done that, nothing helpsI have tried all combinations of wiring and shielding and kits known to man. the digital motors on these TMs play havoc with the Humminbirds. I have 2 on the bow (SI and standard) and both have interferance. The problem is the digital motors actually turn power off and on digitally (really fast) to control the speed, not a variation in voltage (0-36volts). The result is that sometimes, the frequency of the on and off, is close to the sonar frequecy and HB is bad about not filtering this internally. Has nothing at all to do with the actual power wires to the either unit, it is the field around the motor. I have tried everything. I have held the transducer away from the motor and once about an inch away, interferance is gone. Best thing I have found is with the boat out of the water, run the TM from slow to high and watch the graph for interference. Put a Sharpie or tape mark on the TM speed control where the least interference is and then on the water, you can set the speed control in that area. I have a Motor guide and if I thought a TM change would fix it, I would love to use that as an excuse to buy a fourtrex.Hope this helps a little. Milton

I dont know if this will help but it helped mine. My Minn Kota is a Maxxum Pro, not a Fourtrex. I think the Fourtrex has a ground wire running from inside the foot to the head that grounds it. It is supposed to have a fuse. Sometimes it will get corroded and willl not ground properly. Mine did not have this ground wire, so I drilled a small hole in the skeg of my trolling motor foot and attached a small wire which I ran along side my transducer cable and I attached it to the negative terminal of my trolling motor receptacle. I used a small screw to attach the terminal to the skeg and coated it with liquid electrical tape. I also ran a small ground wire from my trolling motor battery (#1) negative post to my starting battery negative post. I now have no interference issues at any speed. From what I understand this doesnt always work, but it has worked like a charm for me. I have an LCX28hd that the screen would completely go out. Now the trolling motor never phases it at all. Good luck and keep us posted on what works.

Ground the shaft to the ground power right where the power goes to the unit. You will have to run a water from shaft to negative power supply.

What I did is drill a 1/8″ hole on the skeg of my Minn Kota and use a sheet metal screw to attach a ring connector to it. Run the wire along the shaft to the negative screw on the trolling motor receptacle and attach. This will ground the trolling motor and should remove the interference. If not, run a small wire from the negative terminal on trolling motor battery #1 to the negative terminal of the cranking battery also. The Fourtrex is suppose to have a fuse in the head of the trolling motor that is the ground. The fuse might be bad or corroded; check this first. I hope this helps, please keep us informed.

I dont understand why the trolling motor companies do not add a ground wire to the lower unit housing when constructing them. I know Minn Kota is doing it for the trolling motors with the transducer mounted in the lowering unit but why not do it for all of them.