Transducer Specs In-Hull

An in-hull transducer, also called a shoot-through or puck transducer, is bonded to the inside of the boat's hull using epoxy or a specialized adhesive. The sonar signal passes through the fiberglass to reach the water below, eliminating the need to drill any holes in the hull. This makes in-hull transducers appealing for anglers who want to avoid permanent hull modifications.

In-hull mounting works exclusively with solid single-layer fiberglass hulls. It does not work with aluminum boats, cored fiberglass (with foam or balsa between layers), or hulls with structural reinforcement in the transducer mounting area. The sonar signal cannot penetrate metal or air gaps within the layup, so confirming your hull construction before purchasing is essential.

Performance is the tradeoff. An in-hull transducer experiences some signal loss as the sonar passes through the fiberglass, reducing depth capability and image clarity compared to a direct-contact transom or thru-hull mount. The degree of signal loss depends on hull thickness — thinner hulls transmit more efficiently. In-hull transducers are generally limited to traditional sonar and CHIRP modes; imaging frequencies are too high to transmit effectively through fiberglass.

Installation involves sanding the interior hull surface smooth, applying a thin layer of marine epoxy, and pressing the transducer firmly into the epoxy to eliminate any air bubbles. Air gaps between the transducer face and hull will severely degrade or completely block the sonar signal. Some manufacturers recommend filling the area with non-toxic liquid (like propylene glycol) to verify signal quality before committing to permanent epoxy installation.