trolling motor interfering with sonar?

[Bubba7827]

I have a 2021 195FSH which I purchased used this past spring.

One of the things I am trying to fix is an apparent interference showing up on the sonar (garmin) when I turn on the trolling motor (minnkota)

I am able to operate the sonar but when I start the trolling motor, the sonar picks up significant noise rendering it not very useful.

I suspect the grounding.

The TM is powered by 2 12v batteries wired as a 24 v system.

The garmin is powered by the house battery.

I am told I need to separate the grounds but I am not sure how to do that. I believe that the two units are currently on the same ground buss.

What does the ground buss go back and connect to? Can I add a second independent ground buss for the TM system?

Hopefully somebody here knows what I should do cuz I am pretty much taking wild stabs here.

But at least I have a good excuse for not catching fish.

 

[CastawayRK]

By “sonar” do you mean the factory thru hull transducer or something else? Does the trolling motor have its own 2 batteries or are the house and cranking battery wired to provide the 24v?
Sidescan is almost always useless when running the trolling motor, a tragic thing I learned after installing it. It will give best vue at 2-3 MPH on the big motor. Traditional sonar and down-scan/down-vu should work by adjusting the noise filters in the unit
Cheers
Randy

 

[CastawayRK]

PS - googling the issue I learned that some generations on MinnKotas have a fuse in a brown ground wire in the head. If that fuse is blown the noise issue is much worse. I found no such fuse in my terrova

 

[Bubba7827]

By “sonar” do you mean the factory thru hull transducer or something else? Does the trolling motor have its own 2 batteries or are the house and cranking battery wired to provide the 24v?
Sidescan is almost always useless when running the trolling motor, a tragic thing I learned after installing it. It will give best vue at 2-3 MPH on the big motor. Traditional sonar and down-scan/down-vu should work by adjusting the noise filters in the unit
Cheers
Randy

By "sonar", I mean the garmin head unit and the transducer - the complete system (I dont think it is factory)

The trolling motor has its own 2 batteries which power nothing else.

Down Vue is the view I am working with. I will look into the noise filters in the unit settings - thanks for the tip.

I have seen the ability to change the sonar frequency in there - is that a potential solution?

And I will look for the fuse. My trolling motor is a RT Terrova Riptide with Ipilot & Spot Lock. Model 1363741

I want to be able to troll and downscan at the same time.

Why is it that the side scan doesnt work with trolling motor but does with yamaha engine? Seems like jet would disturb water much closer to transducer than front mounted trolling motor. Maybe the TM stirs up the water before it gets to the transducer while the jet disturbs the water just beyond the transducer?

 

[CastawayRK]

Exact same troller I have so unless I’m blind you don’t need to look inside the head for resistor.
My understanding is the motor sends out noise that is close enough in frequency to the transducer that it is seen as the echo signal. The big motor doesn’t do this.
If it’s 2 separate batteries I don’t see how it’s ground issue. The heading sensor is Bluetooth to motor so even is it is on house battery it wouldn’t cause a ground issue
I can get a good downvue image with troller. I understand the troller is close to the 1070 frequency than sidevue works on setting the downvue to lower frequency should help. In theory tho you won’t have as high resolution with lower frequency

 

[Bubba7827]

I was reading the manuals and came across a minkota phone number for sonar interference issues. 1-800-227-6433. I think I will give them a call in the hopes it is something they can readily identify and remedy.

 

[CastawayRK]

Please share if you find something helpful. These two pictures show a clear Sidescan image (big motor) and one that shows the interference when troller is running on both down and Sidescan. Switching down scan to lower frequency helped a lot. The aqua quadrant is downscan thru the new GT56UHD transducer the standard sonar below it is using the factory in-hull transducer. The transducer ID is shown below the depth. What transducer are you showing?

 

[CastawayRK]

So I’ve come to learn that the tournament bass fishers use Sidescan to scout structure in advance since running over a spot with big motor isn’t helpful. Then during tournament they approach the spot on trolling motor and look with forward facing sonar to see if fish are there
I am most definitely not a tournament guy. I fish for both bass and stripers. My plan for bass was to scan a location with Sidescan using troller and then double back if spot looks good. Obviously I need a different plan!

 

[RockShawn]

Have you checked to make sure there is a ferrite bead installed on the sonar cable just before it connects to the head unit. The gt56 cable is thin enough that it should be looped through the ferrite bead provided by Garmin to keep it in place.

My old boat was set up almost exactly like your situation with Garmin and Minnkota and i had no issues. But I also had the ferrite bead in place.

 

[CastawayRK]

I don’t have a ferrite bead and one did not come with transducer. A lifetime supply on Amazon is $10 so I’ll give it a shot. Garmin shows looping the cable as in this picture for a different application. Does anyone know if loop is vital?
Thanks

 

[RockShawn]

Loop is required to keep it in place. You want it just a few inches from where the sonar attaches to the head unit. And the cable is too thin for the ferrite bead to close down tightly on it, Well at least with the Garmin ferrite beads.

 

[FSH 210 Sport]

Your trolling motor needs to be on an independent battery bank that is totally isolated from the battery that is powering your MFD including the grounds. So if the ground on your trolling motor bank is connected the house battery ground you need to separate them. That includes battery chargers as well.

The “noise” you’re getting on your mfd is not coming from the trollers prop wash it’s coming from the electric tolling motor itself.

Canon the manufacturer of electric down riggers, also a Johnson Outdoor company who owns Minnkota, advises putting the electric down riggers on their own battery for the same reason, to keep from introducing “noise” into the MFD.

The only time I get any interference on my Solix is when I’m sitting at idle with the main engines running due to the aeration of the water from the jet pumps. Even moving very slowly forward keeps that interference from happening.

 

[CastawayRK]

In my case the trolling motor is on its own batteries whose wires fun from them (mounted on shelf forward in head) directly to motor. There is no possibility of common ground. Correct the interference is caused by EMF from motor not from prop wash.
@FSH 210 Sport do you use side scan? This apparently is almost exclusively Sidescan issue for reasons not clear to me. Maybe since the receiver is picking up a signal sweeping large area instead of just looking down.

 

[CastawayRK]

To add the only electrical stuff powered by house battery near the troller power cables would be bow lights and speakers. I don’t see how interference could be carried through the radio, but I’m going to disconnect bow lights ground just to see if it matters. It is of course connected even when lights are off
Also to point out obviously transducers are at the stern so those cables get nowhere near the troller.
And lastly weird to me is that Forward Facing Sonar mounted on the trolling motor itself does not suffer this issue.

 

[FSH 210 Sport]

In my case the trolling motor is on its own batteries whose wires fun from them (mounted on shelf forward in head) directly to motor. There is no possibility of common ground. Correct the interference is caused by EMF from motor not from prop wash.
@FSH 210 Sport do you use side scan? This apparently is almost exclusively Sidescan issue for reasons not clear to me. Maybe since the receiver is picking up a signal sweeping large area instead of just looking down.

I use side imaging, down imaging and 2D imaging all the time. I will say using side imaging in deep water >40’ doesn’t produce the results that using it in shallower water <40’. I mainly use down imaging and 2D sonar.

 

[Bubba7827]

To add the only electrical stuff powered by house battery near the troller power cables would be bow lights and speakers. I don’t see how interference could be carried through the radio, but I’m going to disconnect bow lights ground just to see if it matters. It is of course connected even when lights are off
Also to point out obviously transducers are at the stern so those cables get nowhere near the troller.
And lastly weird to me is that Forward Facing Sonar mounted on the trolling motor itself does not suffer this issue.

My trolling motor has a GPS locating puck which was installed behind my helm in the same compartment as my sonar. A few weeks back, I moved the puck to a different location close to the trolling motor itself (on top of built in tackle box on 195FSH). I thought the puck might be a possible source of sonar interference but the interference remains.