1. Minn Kota
  2. Trolling Motors
  3. Transducers & Sonar
  4. Interference

Troubleshooting Trolling Motor Transducer Interference

Updated

Interference in a fish finder refers to unwanted signals that can distort the display and make it difficult to accurately read the sonar data. This interference can manifest in various ways, such as noise and clutter. Noise and clutter can appear as random dots or lines on the screen, making it hard to distinguish actual fish or structures.

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Interference

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:
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If you have interference and a Humminbird, you can try adjusting your noise filter

Troubleshooting if you have a Minn Kota motor with DSC or US2

  • If you are not a do-it-yourselfer, you should try to contact your closest Minn Kota Authorized Service Center.
  • If you have a Minn Kota motor with DSC or US2 and you are a do-it-yourselfer, follow the steps below
  1. Confirm the number of sonar depth finder mounted on the boat
    • If more than one sonar depth finder (Humminbird or any other brand), are both depth finders 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 depth finder 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 the next step.
  2. Update Software
    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.
  3. Adjust Filter Settings
    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.
  4. Verify Transducer Plug Connections are secure and check the US2 fuse (if you have US2)
    • Check the connections on the Dual Spectrum CHIRP or Universal Sonar 2 Adapter Cable 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.
      • All 2013 and newer Minn Kota 24 and 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.
  5. 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.
  6. 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 depth finder) 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 have been packed with the cable as of March 1, 2013.
  7. Contact Humminbird
    If you have tried all of the above steps and are still experiencing interference please contact Humminbird's customer service department by clicking here.

Troubleshooting if you have a Minn Kota motor that has MDI, MSI or a Minn Kota motor and non-Minn Kota transducer

  • If you are not a do-it-yourselfer, you should try to contact your closest Minn Kota Authorized Service Center.
  • If you are a do-it-yourselfer and you have a Minn Kota motor with MDI or MSI or Minn Kota motor and a non-Minn Kota transducer, and follow the steps below.
  1. Confirm the number of sonar depth finders mounted on the boat
    If more than one sonar depth finder (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 depth finder 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 the next step.
  2. Update Software
    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.
  3. Adjust Filter Settings
    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.
  4. 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.
    1. This can be done externally by scraping a small amount of paint from the lower unit just behind the external transducer clamp.
    2. 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.
    3. Connect this end of the wire to trolling motor battery negative/ground and to the depth finder battery negative battery ground.
    4. 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 and 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.
  5. 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.
  6. 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 depth finder) 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 have been packed with the cable as of March 1, 2013.
  7. Contact Humminbird
    If you have tried all of the above steps and are still experiencing interference, clicking here to email Humminbird Customer Service.

Additional Troubleshooting for a Mega Side Imaging or Mega Down Imaging product" Additional Troubleshooting for a Mega Side Imaging or Mega Down Imaging product

If you have a side imaging or down imaging product and the above suggestions do not reduce the interference

Contact Humminbird Customer Service with the below information:

  1. If you have a depth finder with a card reader and image capture capabilities.
  2. It would be helpful to include screenshots showing:
    • what the fishfinder display looks like with the trolling motor running.
    • what the fishfinder display looks like while the trolling motor is in the off position.
  3. 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.
  4. Be able to provide the complete fishfinder-related setup on the boat such as:
    • What is the serial number of your Humminbird depth finder?
    • Which fish finder models are installed on the boat?
    • Where are the transducers located for each depth finder?
    • If you have two GPS capable Humminbird fish finders on the boat, are you using either an Interlink or Systemlink to network GPS receivers on the boat, etc?

The proper torque procedure for cables in the field

  • Loosen the connectors. Next, using your fingers only, tighten the connectors to a reasonable level.
  • Draw a line straight across both connector halves
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  • Using Appropriate slip-joint pliers or similar tools, grasp each connector half. Using the above-drawn line as a reference, tighten the connectors an additional 1/4 of a turn.

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