I have an old Humminbird 797SI Combo that I recently moved to my bow. Now the MotorGuide causes interference. Yes, I've done everything H/b has told me to do. I've installed H/B pwr cord with a filter and the ferrite ring. I can move the transducer about 6 inches away from the motor and the interference goes away, but this isn't feasible in the water. I've even tried to insulate the transducer between the motor with 3/8 inches of rubber. Anyone have any solution besides the obvious, get Lowrance or get a Minnekota.

My dad just installed new Lowrance HDS 12s on the front and back. The one in front does the same thing. He has a Minn Kota Fortrex. So they won't help... Would like to know how to fix this as well.

Humminbird says their products are not designed to work with Motorguide

Had the same problem. Tried everything, but what fixed it for me was installing a ground strap in the TM lower unit.

I have the same issue with my Lowrance. Tried everything mentioned in the threads and nothing works. Finally spoke with an on site Lowrance technician and he told me it is possible the bushings in my Fortrex are worn causing electronic "noise". Unfortunately and overhaul of the electric motor or a new trolling motor is the fix. Neither is in my near future.

Thanks I'll try that but where did you run the ground to in the boat ? The trolling motor ground or the Sonar unit ground ?

Call John Jones at Jones Trolling Motor. He may have other ideas too. If he agrees, he can hook you up with the parts and give you an idea on how to do it.

Drill a hole in the skeg of your tm, put a bolt with a washer on each side and 2 hex nuts. Add a circle connector to a 16ga. wire. Run the wire up the tm shaft with zip ties. Run the wire in to where your graph wires run into your bow, wire nut,the 16ga. to the negative if the power cord to your graph, tape it up good. Take a dremel and cut off the extra bolt thread hanging past the 2 hex nuts. Add a dab of marine silicon to each side of bolt to prevent corrosion.

Steve at Steve's Custom Props has a fix and it is only $75.

Thanks to all of you guys. I knew ya'll could help

Thanks guys. I put the ground strap on and while it didn't clear up the interference completely it did take away maybe 75% of it. At least I can use it now with the trolling motor running.

I'd sure be interested in more info on this.

And I have had HB units on a Motorguide for over 3-1/2 years, done all the tricks, still have a bit of interference, but it is not huge.

Just to see if it was going to help before I drilled a hole in the T/M skeg, I ran a wire, from the negative battery terminal that ran the Humminbird(main battery ) then just held it on a bare spot on the tm skeg. With the H/B on SI and the T/M running ,I touched the wire to the bare spot on the skeg,(or any bare spot on the trolling motor) and it cleared up. Just a quick easy way to check if it's going to help.

interesting. never thought about the skeg trick

I had tried everything, from rubber between the transducer mount/tm head, running a ground from negative of crank battery to negative of tm batteries, grounding to the strap holding the transducer mount, No dice. Drilled a,hole in the skeg and presto.

Fyi: only try one thing at a time, undo your last "fix" before trying the next. Two at the same time,can counter each other and yield no results.