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!