A fish-finding or depth-sounding transducer on the bottom of a trailer boat must run a gauntlet of bunks and rollers. Yet, you can minimize problems by choosing the right kind of transducer. Here are the three best types, with some tips on installing them to minimize trailer interference and maximize fish-finder performance.
Flush-Mount Through-Hull Transducers
Unlike conventional through-hull transducers that protrude well below the hull and might require a bulky fairing block, flush-mount through-hull transducers are virtually flat and far less likely to hang up on a trailer bunk or roller. These are available in bronze, plastic and stainless steel through-hull fittings with a 600- or 1,000-watt dual-frequency transducer element imbedded in the middle.
Some flush-mount transducers are designed to shoot perpendicular to the boat’s bottom (0 degrees) and so are best suited for boats with flat bottoms or an aft pad at the transom. For boats with V-bottoms, there are flush-mount transducers with tilted elements (12 and 20 degrees) that aim the signal straight down, even though the through-hull fitting is angled. These ’ducer types require at least a 2-inch-diameter hole for installation.
Though trailer interference is minimized, care should be taken to ensure that the transducer does not rest atop a bunk or roller when the boat is loaded.
Tip: To maximize fish-finder performance, avoid installing the transducer aft of other through-hulls, intakes or objects that might cause air bubbles to stream across the face of the transducer.