How to Troubleshoot a Raytheon L750

The Raytheon L750, made by Raymarine Marine Electronics, is a fish finding device used by deep sea fishermen. The device provides detailed information about the location of fish streams on a large LCD display. For the most part, the device is well-built, but a few common problems may occur. The most typical issues concerning the L750 include a malfunctioning screen due to electrical interference and inaccurate readings. Fortunately, these issues are relatively straightforward to resolve.

Things You'll Need

  • Stiff brush
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Instructions

  1. Malfunctioning Display

    • 1

      Check for electrical noise. Turn off all electronic devices on the boat, including the boat itself. Turn on the L750. Turn on the electronic devices one at a time until the screen starts to malfunction. Reroute the L750 power and wiring cables away from the wiring of the device causing the display to malfunction.

    • 2

      Check all wiring connections. Look for loose, uninsulated and dirty connections. Clean the dirty connections. Re-solder the loose connections. Insulate and protect them with shrink-wrap tubing.

    • 3

      Check the transducer cable (the cable that goes into the water) for water damage and significant bends. Replace the entire cable if it is damaged.

    • 4

      Start the engine in neutral and slowly move out into the water. Watch the display screen while accelerating. Take note of the speed when the display begins to malfunction. Reroute all the L750 wires away from the boat's alternator.

    Inaccurate Readings

    • 5

      Check the mode displayed on the LCD. If the display is flashing "Simulation" on the screen, change the mode to "Survey."

    • 6

      Check the transducer for proper submersion. It's possible that it kicked up as the result of hitting an obstacle, like a rock. Place it back into the water vertically, with only 10 degrees of sway in either direction to receive accurate readings.

    • 7

      Remove the transducer from the water and check the sensor end for debris buildup, such as seaweed or mud. Scrub the sensor end with a stiff brush and put it back into the water.

    • 8

      Check for loose and corroded connections to the power source. Replace or secure the connections to ensure at least 10 volts are sent to the L750 for optimum operation.