Fish finder noise from trolling motor

[moguy1973]

So I just recently installed a Minn Kota Maxxum on my boat and at the same time I installed a Garmin echoMap 54dv on it.  Today I took it out for the first time with that setup.  When I have the finder showing traditional 2D sonar it looks fine until I start the trolling motor.  I then get real thin vertical lines that show up coming off the bottom of the screen.  It's almost like the transducer is picking up the blades on the trolling motor because the lines are equidistant from each other.  The problem is MKs have the skeg on the front of the motor and the Garmin transducer for that unit is HUGE and takes up a majority of the bottom of the rest of the head of the motor and I have it as forward towards the skeg as possible.  Any suggestions?

Picture of the transducer on the trolling motor. 

[fishinwrench]

Are you powering your sonar unit from the TM battery(s) or the cranking battery ?

[moguy1973]

Crank battery.

From looking around it seems the newer digital MKs give off RFI and it sends interference to finders if you have the transducer wiring ran the wrong way.  They say that I can also install a ferrite ring to see if that isolates the noise.  I saw a video where a guy routed his transducer cable along the mounting arm instead of up the shaft to the TM head and then down the TM wiring.  Might try that.

[Dutch]

That choke is about $70.  I had one on my last boat with low & mg.  I will prolly have to do it on this one also.

 

It might also under the deck if the tmotor wiring is close to ro touching the sonar unit xducer cable.

[moguy1973]

37 minutes ago, Dutch said:

That choke is about $70.  I had one on my last boat with low & mg.  I will prolly have to do it on this one also.

 

It might also under the deck if the tmotor wiring is close to ro touching the sonar unit xducer cable.

You can get generic ferrite chokes for a couple bucks on amazon.

[fishinwrench]

I've heard of this problem, even back in the days of Flashers, but I've never had to fight it.  Many units have a suppressor setting or ASP (signal processing) that is supposed to block that type of interference.

[176champion]

I have heard that putting a piece of rubber between trolling motor and transducer mount will help eliminate the noise..i have a piece of rubber hose between my transducer mount and trolling motor and don't seem to have any issues on my helix 7..