Overview

Fish finder interference can cause inaccurate depth readings, fluctuating numbers, distorted sonar images, or intermittent loss of bottom readings. These issues can be caused by several factors, including interference from another sonar unit, electrical noise from onboard equipment, or turbulence and air bubbles around the transducer.

Understanding the type of interference you're experiencing is the first step toward identifying the cause and correcting the problem.

This guide covers the most common causes of fish finder interference and provides troubleshooting steps to help restore reliable sonar performance.

1. Sonar Cross-Talk from Other Fish Finders

Sonar cross-talk occurs when two or more sonar units are operating simultaneously within the same general area. Each unit transmits acoustic signals through the water, and another unit may receive those signals as interference.

This can happen even when the fish finders are different brands or operate on different frequencies. Moving the transducers farther apart or changing frequency settings may help in some situations, but it does not guarantee that interference will be eliminated.

Common symptoms include:

• Incorrect or fluctuating depth readings.
• Sudden changes in displayed depth that do not correspond to actual water conditions.
• Erratic sonar readings when another fish finder is operating.
• Interference that disappears when the other sonar unit is turned off.

Troubleshooting:

1. Turn off all other fish finders and sonar equipment on the boat.
2. Operate the HawkEye unit by itself and observe whether the readings stabilize.
3. Turn the other sonar equipment back on and check whether the interference returns.
4. If the problem occurs only when multiple sonar units are operating, cross-talk is likely the cause.

In situations where two sonar systems interfere with one another, operating only one sonar unit at a time is generally the most reliable solution.

For additional information, see our article: Sonar Cross-Talk.

2. Electrical Interference from Onboard Equipment

Electrical interference can occur when other electrical devices on the boat introduce unwanted electrical noise into the power supply or wiring used by the fish finder.

Common sources include:

• Trolling motors.
• Bilge pumps and livewell pumps.
• Electric motors and other high-current equipment.
• Poor electrical connections or grounding.
• Electrical systems with inadequate power supply isolation.

Electrical interference may cause unstable readings, erratic display behavior, or intermittent operation.

Troubleshooting:

1. Turn off other electrical equipment, such as trolling motors, pumps, and other accessories.
2. Observe whether the fish finder readings improve.
3. If the problem stops, turn the equipment back on one device at a time to help identify the source.
4. Inspect the fish finder's power connections for loose, corroded, or damaged wiring.
5. Where possible, test the fish finder using a clean, independent 12V power source to determine whether the boat's electrical system is contributing to the problem.

If electrical noise is confirmed, improving power connections, isolating the source of interference, or using an appropriate 12V power noise suppressor may help.

For additional troubleshooting instructions, see: Troubleshooting Erratic Readings Caused by Boat Electrical Interference.

3. Transducer Turbulence and Air Bubbles

Not all fish finder interference is electrical or sonar-related. A transducer that is exposed to turbulence or aerated water can also produce inconsistent readings.

When a boat is moving, water flowing across the hull can create turbulence and air bubbles. If these pass across the transducer face, they can interfere with the sonar signal.

This is especially common when a fish finder works correctly while the boat is stationary or moving slowly but loses its bottom reading as speed increases.

Common symptoms include:

• The unit works properly at idle but loses depth while underway.
• Readings become inconsistent as boat speed increases.
• The fish finder intermittently loses the bottom.
• Performance improves when the boat slows down.

Troubleshooting:

1. Inspect the transducer mounting location.
2. Check for nearby hull features, strakes, steps, fittings, or other obstructions that may create turbulence.
3. Make sure the transducer is mounted at the correct height and angle according to the installation instructions.
4. Confirm that the transducer face remains in clean, uninterrupted water flow while underway.
5. If necessary, consider relocating the transducer to a location with cleaner water flow.

For additional guidance, see: Top 5 Transducer Installation Issues.

4. How to Identify the Cause of Fish Finder Interference

The following troubleshooting guide can help narrow down the source of the problem.

5. Still Experiencing Interference?

If you have completed these troubleshooting steps and are still experiencing problems, our technical support team can help narrow down the cause.

When contacting us, please provide the following information:

• The HawkEye model number.
• A description of the issue and what the display is showing.
• Whether the problem occurs while stationary, underway, or both.
• Whether other fish finders or electrical equipment are operating at the same time.
• The make and model of any other sonar equipment installed on the boat.

This information will help us determine whether the issue is related to sonar cross-talk, electrical interference, transducer installation, or another factor.

HawkEye Electronics Technical Support
We're here to help you get back on the water with reliable depth readings and dependable sonar performance.