It is with good reason that marine electronics manufacturers build transom mounted transducers. They simply provide the easiest installation and deliver the most effective signal for sail, rowed/paddled, outboard and I/O powered boats. Installed, transom-mounted electronic transducer equipment is readily accessible, relatively easy to change, adjust and to service and they are, by far, the most popular. However; they are not without inherent problems... leaks--slow, damaging, costly leaks.
Conscientious boat owners are justifiably reluctant to mount their transducer equipment to the transom. Trepidation is quite normal; perhaps they've previously experienced hull leaks of some sort and the resulting damages, or read about them, or maybe due to just good 'ole common sense they'd prefer to err on the side of caution. After all, the mounting holes are below the waterline. The idea of having to drill holes below the waterline can be unnerving, and some boat owners just won't do it; neither will many professional installers.
Installation instructions that accompany fish-seeking transducers are generally very well-written by the most respected names in the industry, and they stress the importance of sealing the screw holes. Regardless, once screw holes are drilled there is not much else to do except your best job caulking the screw holes and mounting your transducer. And are they really sealed? You most likely won't know for some time.
Once the holes are drilled you're on your own. Any water-intrusion problems created by the installation of transom-mounted transducers, or any other below-the-waterline-accessories, most assuredly will not be covered by your boat warranty or your insurance. Once the transducer is mounted, it will generally require multiple trial and error adjustments, requiring the caulk on the screw seals to be broken and re-caulked each time in an attempt to optimize a perfect signal.
Finding out later that you have taken on an inordinate amount of water in your hull is more than enough to ruin anyone's summer. Water intrusion into a hull can cause excess water weight, absorption, rot, mildew, discoloration of your boat hull, or osmotic blistering (chicken-pox-like gel coat blisters). In climates that experience winter freeze, water held in a hull can freeze, expand, and break loose the stringer system. The stringer system is the structure that joins the floor and the hull of the boat, providing its foundation for support and rigidity. Repair to these types of damages can become cost prohibitive.
In response to the demand for the best installation method for a transom-mounted transducer, all types of transducer mounting accessories have evolved. There is the polyethylene cutting-board-type material which comes in all shapes, sizes and colors designed to mount one or several electronics. They come packaged with mounting screws...yes, to screw right into your boat transom. There are unwieldy rods, brackets with suction cups, clamp-on mechanisms of all manner, and other types of regalia that hang over the gunwale of your boat. Some folks will go so far as to glue a block of wood to the transom...anything to avoid having to drill holes in the boat below the waterline.
Boats are expensive and they provide memorable experiences and pleasures for families and fishermen worldwide. Boaters are keeping their boats longer and maintaining them better than ever before. It just is not always necessary to drill your boat full of holes and risk water intrusion. Boat owners have a choice when transom-mounting their fish-finder sonar transducers.
