Topic: grounding question

[Nela]

Ok, I recently installed a 859ci HD DI on the bow of my boat and an 899ci HD SI DI on the console. I getting some electrical interference on the 859, only. Both units are connected to my cranking battery and I believe the interference is coming solely from my trolling motor. I was told that if I connected a ground wire (6 guage or better) from my trolling motor batteries to my cranking battery it would eliminate this interference. This is coming from a boat mechanic that claims to regularly install depth finders. I have an 80 pound thrust, 24 volt trolling motor on my boat. Those batteries are connected, in series, to give me the 24 voltss needed for the troling motor. How would running a ground wire from the negative post of one of the trolling motor batteries to the negitive post of the cranking battery help? Am I missing something here?


nela

[bobcoy]

It makes the grounds equal. Using the large guage wire is necessary. It may or may not help your situation. The trolling motor interference may be due to the TM power wires being too close to the transducer wire or any of the wires in the area. I would first put more distance between the TM Power wires and the wires from the fish finders. The trolling motor power wires go to the foot pedal on cable steer motors as well as to the TM plug. If the transducer wire or power wire are close at any point try to separate as much as you can. Humminbird uses ferrite rings to help that situation also. Call them and tell them what you are experiencing and they will probably send you rings,no charge Bob

[N9Phil]

The first thing is to look at  this FAQ fro Humminbird on the subject
http://www.humminbird.com/Category/Support/FAQ/Trolling-Motor-Interference/

After you have done this you might call Humminbird Customer Service and have them send you a Ferrite ring. Run your transducer cable 6-8 passes through the center of the ring.  The last resort that we learned at a recent workshop presented by Dr. Jason Halfen is to connect a wire from the bottom of the trolling motor (Skeg) run up the side of the shaft and connect it to the Ground of the cranking battery.
http://www.thetechnologicalangler.com/

Phil