"Through-hull" Transducer
(often confused in terminology with the "shoot-through" the hull transducer)
"Transom-mounted" Transducer
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3 Types of Boat Transducers - Marine Transducer Installations
Nanticoke Maritime LLC
214 295 5733
General description of a marine transducer: A marine transducer is best described as an electronic sonar device mounted to a vessel that converts input signals of one kind into output signals of another kind, such as sound waves to electrical waves. In the case of fish-finder or depth finder transducers, an electronic ping sounding is emitted from the transducer, bounces from an object which it intersects, and is instantaneously received by the transducer. An image below the boat is detected from the emitted and returned “pings” and is translated to an electronic image recorded by the onboard electronics, oftentimes in the form of an image. The result is generally made visible on the screen of an on-board monitor. Boaters and fishermen use transducers mounted on or in their boats to detect images of fish, bottom structures, topography, depth of water and generally aid in navigation by locating images below the bottom of a boat. And, of course, there are many different types and models of equipment to suit most any user requirement. Many boat owners and fishermen are now equipping their boats with multiple transducers and electronics which perform various functions. The method and type of mounting a transducer used on boats oftentimes becomes very confusing. There are typically only 3 types of methods of mounting a transducer in a boat. Transducer mounting and adjustment problems comprise the majority of all marine electronics troubleshooting issues.
The Candid Truth About Each of 3 types of (high speed) Transducer Installations
The "transom-mounted" transducer is externally mounted on the transom whereby the face of the transducer makes contact with the water. Typically, these are the most effective, the easiest to service, to adjust for an optimum sounding, easily replaceable and, of course, the most popular. This type of transducer mounting allows for maximum performance of your electronic equipment as designed by its manufacturer. To mount a transom-mounted transducer, screw-holes are required by drilling holes below the waterline of your boat. Review and understanding your boat warranty disclaimers and the disclaimers made by the electronics manufacturer should be considered before mounting this type of transducer. Many boat owners and boat dealers are justifiably reluctant to mount transom-mounted transducers. Oftentimes they can be very difficult to adjust properly and generally will leak when you least expect it. There is an abundance of advice on "how to drill holes in the hull of your boat" to mount a transducer. Removing transducer mounting screws is a "surefire" way to determine if there is any water in your boat hull. Transducers generally found mounted on the transom of a boat may include high speed transducers, Side Imaging (Si), Structure Scan and Down Imaging Transducers. Unobstructed contact with the water is the accepted formula for optimizing a transducer's full potential. It is not uncommon to find many screw holes in the transom of a boat made by boat owners simply by changing equipment or seeking a different location to avoid bubbles....all of which can devalue your boat, It's a good idea to understand exactly what you're getting into before chucking up your favorite drill bit. Ask your dealer for his written liability statement before he begins installation....that will give him something to think about!
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"Shoot-through" the Hull Transducers
(less commonly referred to as an "in-hull" transducer, amongst other nondescript terms)
The "Shoot-through" the hull type transducer is mounted inside of the hull, usually in a bilge, sump or keel, permanently adhered to the cockpit side of the hull with an epoxy or may be contained in a liquid reservoir. The sonar ping emitted from the transducer must adequately penetrate a solid unblemished hull material. Hull material actually will absorb or muffle much of the sounding from a transducer. There must be no voids in the layers of glass layup, no uncured or dry glass mat or resin bubbles to muffle (all of which you will never know until after you install your "shoot-through"), thwart or distort the emitted sounding...something like "shouting into a pillow". Adhesive medium used to secure the transducer in these types of installations actually increase adverse acoutics through which the "ping" must penetrate. The return "ping" must also transmit on its return trip through the hull and adhesive medium. The transducer has no contact with the water outside of the boat. "Shoot-thrus" are generally installed to avoid the necessity of making screw-holes in a transom below the waterline, for protection, and in most instances, will reduce or compromise the effectiveness of the transducer sounding. Other compromises are made in regards to eliminating a speed wheel, if equipped, and recording water temperature. Unlike the easily maintained and adjustable transom-mounted transducer, this method of mounting is generally fixed in place with a bonding material and cannot be adjusted, serviced or changed without the likelihood of destroying the transducer during removal. The user generally will install his transom-mount designed transducer in this manner and will settle for reduced performance as a compromise to sacrificing his boat hull as a "trade-off" for screw-holes and leaks and, of course, it may not work at all. To remove it and to try something differnt, you'll likely destroy it. There is an abundance of advice on "how to install a shoot-thru".
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The transducer "Through-Hull" is permanently installed in a "through-hull" hole on the bottom side of the boat hull whereby the face of the transducer is in direct contact with the water. It is usually “faired” to the hull deadrise (angles) so as to cause its beam to be parallel to the surface of the water. This transducer is fixed, cannot be adjusted, and is most always found on larger boats. They are usually the most expensive to purchase, to install and to replace and seldom are found on trailer boats. The "through-hull' transducer generally can be vey efffective when installed properly and faired true. These are the most permanent of all types of transducers. Installation is best left to one well versed in this type of installation.
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Nanticoke Maritime LLC
"Transom-mounted Transducer"
"Shoot-through-the-hull Transducer"
"Through-hull" Transducer"
A NOTE ABOUT "SHOOT-THROUGH" TRANSDUCERS and ALUMINUM BOAT HULLS: Boat hulls built of aluminum and other metals are dense and reverberate an echo out of tune from pulsations made and returned by your transducer causing erratic feedback....something like "shouting into a cavern". The return signal can easily become "confused" and misinterpreted when converting it to an electronic "language" observed as "garble" on your monior. Transom-mounted transducers correctly mounted on aluminum boat hulls can be effectivley optimized according to the manufacturer's specifications and are recommended.
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