How to Read a Ratheon L-365 FishFinder

How to Read a Ratheon L-365 FishFinder
The Raytheon L-365 Fish Finder is an electronic device that uses sonar waves to receive information about lake or ocean depth, where schools of fish are, obstacles in the water and water temperature. The L-365 comes with a transom mount, transducer and installation kit, cables and display screen. The unit's display uses 240x64 lines of resolution and a 300 watt output. Learning how to read and interpret the screen display requires a little time with the unit.


Difficulty: Moderately Easy

First Screen

Things You’ll Need:
  • Raytheon L-365 Fish Finder
  • Boat
Step 1
Press the power button to turn on the unit and bring up the screen. Find the power button on the upper right side of the unit. Press power again quickly to adjust the screen display's brightness for the light conditions on the boat. The "Lamp Display" screen will appear. Press either the left arrow button to turn down the brightness, or the right arrow to turn up the brightness. Press power again quickly to return to the main display screen.
Step 2
Press the right arrow button once to bring up the drop-down menu and the "Fish Finder" display screen. The upper left corner shows the speed of the boat and water temperature (displayed in the default Fahrenheit). Look for small fish icons throughout the space under the display information. Use this information to determine where the fish are and at what depth. Read the number under the fish icon. This is the depth (in feet) of the fish under the boat.
Step 3
Press the right arrow button once to use the zoom function. All information displayed on the screen is the same as the screen prior to zoom in function.
Step 4
Read the large number under the lake or water bottom bars. This number is the lake depth at the present moment. Look at the top of the display screen for a small boat icon. This is where your boat is in relation to the fish and water bottom.
Step 5
Look for small black arches in the water between the bottom and the boat when the unit is receiving at 200mgz (displayed in the upper left corner). These are either single fish when there is one present or a school of fish when several arches are together.
Step 6
Read the water bottom surface by looking for a skinny black line, thick black line or a series of pixels and triangles. The thin line represents a hard bottom, thick line a muddy bottom, and the pixels and triangles a ricky bottom.

Tips & Warnings

Print and laminate a copy of the instruction manual's legend and set it next to the unit when fishing to reference while learning the display system.

Article Written By Eric Cedric

A former Alaskan of 20 years, Eric Cedric now resides in California. He's published in "Outside" and "Backpacker" and has written a book on life in small-town Alaska, "North by Southeast." Cedric was a professional mountain guide and backcountry expedition leader for 18 years. He worked in Russia, Iceland, Greece, Turkey and Belize. Cedric attended Syracuse University and is a private pilot.

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