COMMON GROUND

I have 3 HDS gen3 networked with Eithernet and NEMA 2000, Ulterra 24 volt, separate 2 bank charger for the 24 volt system and 1 bank for starting battery. Also Point 1 and Heading sensor for Blue Tooth Ulterra. The locators, Point 1, Nema and Heading sensor are wired to the fuse block. I also have a Vantage trolling motor. Both trolling motors are run of the same 24 volt system. I have 2 60 amp breakers, 1 for each trolling motor. Everything is wired properly. This is on a Lund 2015 Lund Pro Guide 1875, 90 Merc.

I’m getting interference on the Structure Scan when running the trolling motor, not the regular sonar. Also have a Total Scan transducer. I read some post on common grounding the batteries. What I found on the Motor Guide web site was DO NOT GROUND 24 volt or 36 volt to a 12 volt system.

Any suggestions on getting rid of this interference. I also reran the U2 sonar cable away from the power cable and put Ferrite Chokes on all cables. Still getting interference.

Thanks for any help.

I would try a filter on the power line of the graph, kinda like we used to do back in the day with car radios and engine noise. Unless the interference is not electrical but ultra sonic like the transducer is picking up junk from the motor in the water. Try lifting the motor out of the water while its happening, if the interference goes away then its picking it up from the motor in the water. That’s how I would approach it.

Thanks but I found the problem. It was the 3 amp mini fuse. Went through 3 fuses before I found a good one. They all looked good but were bad. Must have been a bad batch. Picked up a box of 6 at Napa.

Hopefully that works for you but it sounds like it might just be a coincidence.

What is the power source for the fuse block that powers the depth finders? They should be sourced to the main starting battery and not to the trolling motor batteries.

There should not be a ground plane on a boat, with the exception of marine antennas, and I think they go to a common ground port, not to the boat itself. So ignoring the marine radio antenna, I don’t think there should be a ground in your system. Just wired directly to batteries or through fuse blocks which are wired direct.

All 3 locators, Point 1, heading sensor and Nema are wired to the factory fuse block with separate fuses and grounds. I didn’t notice this problem untill I got the motor back from Minnkota. They installed a new board and spot lock under warranty. I checked all the connections, maybe something was loose and kept shorting out the the fuse. It’s working now, hopefully it keeps working.

I ran a Terrova 24V, 80 lb thrust on my boat, I decided to upgrade to the new Ulterra Riptide (Saltwater, Just wanted the white color and thought saltwater might Be tougher) First trip out, every time I turned on spot lock, the screen on my Lowrance HDS 10 would fill up with heavy vertical bars and I could not see my jig or the fish. I only jig and it is imperative that I stay still and on top of fish.I tried everything from ferrite beads, trolling batteries run only the trolling motor and I use an exterior rear transducer. I sent it back to Minn kota and asked if I could get it exchanged for a terrova riptide instead. This was done and it does the same thing. If I put the old terrova on, there is no interference. Saltwater versions don’t have a fuse and ground wire under the head, just the neg/pos wires.Any ideas?

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I wired the locators and point 1 direct to the starting battery. Still got interference when I turned on the spot lock so I disconnected the front transducer and it went away. I never fish in the front of the boat anyways so I decided to just remove the front locator all together. For that kind of money you would think Minnkota could fix this problem. Never had a problem with my old Terrova.