The Lowrance X-4 Pro Sonor, Hummingbird's PiranhaMax 180, the Eagle FishEasy 350c, the Lowrance 4X DSI and the Lowrance Mark 4 GPS/Sonar are inexpensive high-quality fish finders. Most fish finder manufacturers produce all high-quality products. The expense of a particular unit is usually based on the features it has.
At under $100, the Lowrance X-4 unit has the lowest price of the group, as of 2015. Its transom mounted transducer supplies 60-degree coverage down to 600 feet deep. The 4-inch SuperTwist liquid crystal grayscale display is fully readable in sunlight.
The Hummingbird PiranhaMax 180 has a triple beam transducer with 1,600 watts of power. It sports over 180 features, as well as Fish ID, fish alarms, depth alarms, zoom and other options. Eagle's budget unit has a 3.5-inch color LCD display, a water temperature feature and its COLORLINE technology defines the composition of the bottom.
The Lowrance 4X DSI also has a 3.5-inch color display and uses a 2,800 watt peak-to-peak dual downscan transducer with a 200-foot maximum depth. The display can help differentiate between predator and bait fish, the thermocline and structure most 2-D sonar units don't define.
The Lowrance Mark 4 GPS/Sonar incorporates many of the other unit's features and adds Global Positioning System technology with a 16-channel antenna. It is compatible with LakeMaster, Navionics, and Fishing Hot Spots charts.