Transom-mount transducers are often the least expensive and easiest way to avoid trailer issues, because they’re usually aft of bunks, rollers or crossbars. Most transom-mount units come in 600-watt dual-frequency versions, as well as 1,000-watt CHIRP models.
The position, depth and angle of adjustment is critical to minimize interference from engine noise and water aeration. All transducers need to run in water free of turbulence. Also, transom-mounts are more prone to breakage from striking an object, though most have a bracket that lets the tranducer kick up.
Tip: Transom-mount transducers should be mounted on the starboard side on single outboard- or sterndrive-powered boats (with right-hand rotation props) or in between twin engines to help avoid interference caused by turbulent water.