Sonar units need transducers to function. Airmar Technology has some general recommendations for inshore/nearshore vessels that pair with many common multifunction displays.
This medium-frequency chirp-ready transom-mount unit is budget friendly. The 300-watt transducer covers the 95 to 155 kilohertz band with beam widths from 26 to 17 degrees, offering good bottom coverage and shallow to mid-depth performance.
A 600-watt tilted-element, through-hull transducer that covers the 130 to 210 kilohertz high-frequency band, with beam widths from 15 to 9 degrees, this chirp-ready unit provides detail of fish holding close to structure and the bottom.
With a constant 25-degree beam in a high-frequency band (150 to 250 kilohertz), this option provides optimal detail of the bottom, fish and baitfish around structure, plus a coverage area roughly 22 feet in diameter at 50 feet of depth. A power rating of 1 kilowatt means more power on target (sounder dependent) for even greater detail.