Trolling motor manufacturers are able to produce a more efficient trolling motor relative to power management.  In doing so, the motors sometimes introduce electrical noise into other electronics on the boat. This noise can be exhibited in several different ways:

  • Random targets/pixels on the display, when the trolling motor is in use.
  • Noise seen on the display, when the trolling motor is in use.
  • The Depth Sounder turns off, when the trolling motor is in use.
  • The Depth Sounder will stop operating, the display seemingly freezing, and will not respond to any button/knob selections, when the trolling motor is in use.
  • Erratic depth readings when the trolling motor is in use.
  • Loss of depth readings when the trolling motor is in use

Below are some examples of what this interference might look like:

 TMI-SI  TMI-SI2
(click images to enlarge)

If you have a Minn Kota motor with US2 and you are a do-it-yourselfer, please follow these steps: 

Step 1. Confirm the number of sonar units mounted on the boat – If more than one sonar unit (Humminbird or any other brand), are both units running sonar at the same time? If the answer is yes, turn the sonar off of the unit that is not on their trolling motor. Does this solve the problem? If yes, this is sonar to sonar interference. There is nothing that can be done about this other than to only run one sonar unit at a time. Some models/software versions have the ability to tap the power button and a screen will pop up showing Sonar, Light and Background Menus. From the Sonar menu, you can turn Sonar off by using your left cursor button. When you are ready to turn the sonar back on you just tap the power button and right cursor to turn it back on. If the answer to either of the above questions is no, then please continue to Step 2.
Step 2. Update Software, Adjust Filter Settings - Always make sure that you have the most up to date software installed in your Humminbird depth finder. Go to www.humminbird.com to login and download the software for your depth finder. You can also try adjusting your depth finders Noise Filter to attempt to decrease the interference, adjusting the Sensitivity may also help. If you have more than one transducer make sure only one is in use. Using two transducers at the same time could cause interference.
Step 3. Check US2 Fuse and Connections - Check the connections on the Universal Sonar 2 Adapter Cable (MKR-US2-8) connecting the trolling motor transducer cable to the depth finder. There is also a transducer cable connection located in the control box under the top cover. Even though the two ends are connected, they MUST be screwed tightly together to eliminate interference. Ensure that the knurled ends are tight. US2 models also have a brown ground wire with a mini 3 amp fuse, if this fuse is blown then this could be the cause of the interference. The fuse should be tested with a digital V.O.M. Replace the fuse, if needed and retest.

 Fuse location inside Motor HeadMotorFuse 

 US2 Cable inside motor headUSCableConnections 

 External US2 Cable the hooks up your unit adapter  US2Connection2
 

All 2013 and newer Minn Kota 24 & 36 volt freshwater trolling motors will include a factory installed fused ground wire.   Note: If this fuse is blown, a circuit loop is being completed through the ground wire. This indicates that an improper power connection is being made to either the motor or depth finder. This improper connection must be located and corrected to prevent a circuit loop and further interference issues.

Step 4. Check wiring - Make sure the deep cycle/trolling motor batteries are not linked to the Cranking Battery. Disconnect chargers, Perko switches, and anything else that may link the two sets of batteries. Try to keep the depth finder power cable away from the trolling motor power cable when rigging. It is also recommended that the excess length of power and transducer cables not be coiled. If you find that interference is still present then you might try using a separate small 12 volt battery to power the depth finder and retest.
Step 5. *Add Chokes - If the interference is still present then you may need to add the Humminbird PC-11 Power Cable (if it did not come with your unit) and the US2 Ferrite Ring (470085-1). If your trolling motor is a PowerDrive V2 or Terrova model you can also add the Ferrite Bead (2887313) to the positive and negative motor output leads on the coil cord closest to the control board. *All 2013 Terrova and PowerDrive V2 models will include a factory installed Ferrite Bead.  All Humminbird Side Imaging units have come with the PC 11 for several years and most Down Imaging units are being packed with the cable as of March 1, 2013. 
Step 6. Contact Us - If you have tried all of the above steps and are still experiencing interference please contact our customer service department directly at 800-633-1468 or by clicking here to email us.
 

If you have a Minn Kota motor that is Non-US2 and you are a do-it-yourselfer please follow these steps: 

Step 1. Confirm the number of sonar units mounted on the boat – If more than one sonar unit (Humminbird or any other brand), are both units running sonar at the same time? If the answer is yes, turn the sonar off of the unit that is not on their trolling motor. Does this solve the problem? If yes, this is sonar to sonar interference. There is nothing that can be done about this other than to only run one sonar unit at a time. Some models/software versions have the ability to tap the power button and a screen will pop up showing Sonar, Light and Background Menus. From the Sonar menu, you can turn Sonar off by using your left cursor button. When you are ready to turn the sonar back on you just tap the power button and right cursor to turn it back on. If the answer to either of the above questions is no, then please continue to Step 2. 
Step 2. Update Software, Adjust Filter Settings - Always make sure that you have the most up to date software installed in your Humminbird depth finder. Go to www.humminbird.com  to login and download the software for your depth finder. You can also try adjusting your depth finders Noise Filter to attempt to decrease the interference, adjusting the Sensitivity may also help. If you have more than one transducer make sure only one is in use. Using two transducers at the same time could cause interference.
Step 3. Add Ground Wire - Adding an external ground wire from the Minn Kota lower unit to the trolling motor battery negative/ground and depth finder battery negative/ground will help prevent interference. This can be done externally by scraping a small amount of paint from the lower unit just behind the external transducer clamp. Attach an 18 gauge wire to the bare spot under the clamp then run the wire up the trolling motor shaft with the transducer wire. Connect this end of the wire to trolling motor battery negative/ground and to the depth finder battery negative battery ground. Experiment with disconnecting trolling motor ground and depth finder ground one connection at a time to determine the connections that result in the least amount of interference.

 *All 2013 Minn Kota 24 & 36 volt freshwater trolling motors will include a factory installed fused ground wire.  Note: If this fuse is blown a circuit loop is being completed through the ground wire. This indicates that an improper power connection is being made to either the motor or depth finder. This improper connection must be located and corrected to prevent a circuit loop and further interference issues. Note: Do NOT run the external transducer wire down the cable jacket to the foot pedal. It should be routed along the mount.

Step 4. Check wiring - Try to keep the depth finder power cable away from the trolling motor power cable when rigging. It is also recommended that the excess length of power or transducer cables not be coiled. If you find that interference is still present then you might try using a separate small 12 volt battery to power the depth finder and retest.
Step 5. Add Chokes - If the interference is still present then you may need to add the Humminbird PC-11 Power Cable and the US2 Ferrite Ring (470085-1). If your trolling motor is a PowerDrive V2 or Terrova model you can also add the Ferrite Bead (2887313) to the positive and negative motor output leads on the coil cord closest to the control board. *All 2013 Terrova and PowerDrive V2 models will include a factory installed Ferrite Bead.
Step 6. Contact Us or your nearest Minn Kota ASC - If you have tried all of the above steps and are still experiencing interference please contact our customer service department directly at 800-633-1468 or by clicking here to email us.
 

Follow the steps provided below to confirm and reduce this interference on other brands of trolling motors if you are a do-it-yourselfer:

 Step 1.   Power the Depth Sounder on in the Start Up mode (normal on the water operational mode) with no other equipment or motors running. Confirm that  the interference is being produced by the trolling motor by establishing that the interference only happens when the trolling motor is used. Some trolling motors may only produce interference when used at certain speeds, so test at as many speeds as possible.
 
Step2.  Once trolling motor interference has been confirmed, you may need to adjust your power connection to the battery as follows:  For boats that have a 24-volt or 36-volt trolling motor, confirm that the depth sounder is powered off the boat’s cranking battery. 

 
Step 3.  In those Humminbird products that have a Noise Filter in the Advanced Sonar Menu, confirm that this is turned ON.

Step 4. You can connect a light gauge wire (18 gauge is acceptable) from the negative post of the trolling motor battery to the negative post of the engine's cranking battery.  It is recommended that you install a 1 or 2 amp inline fuse in this ground wire.  If the interference is still present, check the routing of the depth finder and trolling motor battery leads.  If they run parallel to each other for any length of distance, separate the leads as much as possible or run the leads to the trolling motor and depth finder on opposite sides of the boat.  If interference persists, check the mounting location of the transducer.  If it is mounted external on the motor's lower unit, try temporarily moving it away from the lower unit while operating the motor.  If the interference is reduced or eliminated during this exercise,  you should try to reduce the RF interference by taking a ground wire and connecting it to the trolling motor lower unit.  Grounding the motor case creates a sheild between the motor brushes and the transducer, trapping or shunting the RFI to the ground. 

To ground the motor case externally, drill a small diameter (1/8") hole in the motor skeg.  Attach one end of the ground wire at this point by using a self tapping stainless steell screw and run 18 gauge wire up the motor shaft along with the transducer cable.  Connect the other end of the ground wire to the Humminbird unit's negative battery lead or post. 

If you have a side imaging or down imaging product and the above suggestions do not reduce the interference; contact our Customer Service Department with the below information:
 
 1.  If you have a unit with a card reader and image capture capabilities, it would be helpful to email us a Screen Snapshot showing what the fishfinder display looks like with the trolling motor running and while it is in the off position.
 
 2.  Be in a position to tell the representative if the interference you are experiencing is occurring on traditional sonar, down looking sonar or side imaging sonar   (if your model is a side imaging unit) or on all types of sonar.
 
 3.  Be able to provide us with the complete fishfinder-related setup on the boat such as:

  * What is the serial number of your Humminbird unit?
  * Which Fishfinder models are installed on the boat?
  * Where are the transducers located for each unit?
  * What trolling motor Brand and model is on the boat?
  * If you have two GPS capable Humminbird fishfinders on the boat are you using either an Interlink or Systemlink to network GPS receivers on   the boat, etc?
  
If you are not a do-it-yourselfer, you should try to contact your motor manufacturers closest ASC.

Here is a brief video on this topic. 

Customer Service 
Toll Free:  1-800-633-1468
service@humminbird.com