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Guide to Marine Transducers

Scuba Steve's Marine  offers an wide range of matched, high performance, high speed transducers for its various depth sounders. There are transducers for virtually every type and size of boat -- sail boats, large power boats, "trailerables" and more. There are also separate sensors you can install that will read your boat speed and the surface water temperature.

We can recommend the best type of transducer for your boat; we will make sure it matches your sounder; and he can help you install both your transducer and your sounder. For do-it-yourselfers, installation instructions are available for all our transducers. To help make your transducer selection easier, we have provided a general guide to the basic types of transducers along with a brief description of where and how to install each.

TRANSOM MOUNT TRANSDUCERS As the name indicates, this style of transducer mounts on the transom. The best mounting location is at the bottom of the transom with the face (bottom) of the transducer on a nearly horizontal plane, as shown in these two diagrams. Installation is best accomplished while the boat is out of the water. The objective in mounting this style of transducer is to keep the face of the transducer in the water -- whether the boat is at rest or underway -- while minimizing the amount of transducer protruding below the bottom of the boat -- as illustrated here.

It is important to minimize the turbulence and aeration around the transducer. Consequently, you should avoid locating the transducer along strakes, behind thru-hull fittings or other hull irregularities that may disturb the water flowing across the transducer face. Transom mount transducers are often used on trailerable boats, as the location does not usually interfere with the trailer bunks, rollers, struts and other objects on a boat trailer. This style of transducer is also used on boats that cannot easily accommodate a thru-hull fitting on the bottom of the boat.

THRU-HULL TRANSDUCERS When properly installed, this type
of transducer offers better performance and fish detection than any other style. As the name implies, it does require drilling or cutting a hole in bottom of your boat. For this reason, installation should be undertaken while the boat is in dry dock. The location of the transducer depends on the type of hull, as shown in these diagrams for displacement and planing power boats as well as fin keel and full keel sail boats. When mounting on a deadrise angle -- such as shown on a full keel sail boat -- a special "fairing block" is required, so that the face of the transducer lays on a horizontal plane.

As with any other transducers, thru-hull types should be mounted where they will be continuously immersed in undisturbed water. Objects than can disturb the water flow around a thru-hull transducer include strakes, fittings, keels and propeller wash. To eliminate potential leaks, it's essential to apply a liberal amount of a quality bedding compound -- one that can stand up to continuous immersion -- around the transducer's stem and fittings on both the inside and outside.

"SHOOT THRU" TRANSDUCERS This type of transducer fastens inside the boat hull, transmitting and receiving signals through the hull material, as shown in this illustration. This works only through fiberglass and is how "shoot thru" or "in-hole" transducers get their name. This style does not require cutting a hole in the bottom of the boat. As with other transducers, location is critical to performance. Typically, a flat section in the aft bilge area is the best spot, although you may need to experiment to find the best location. The latest in hull transducers, the P-79® allows you to compensate for the boats dead-rise angle. Not all boats are well suited to shoot-thru style transducers. On smaller boats, for example, there is often a layer of foam flotation material between the deck and the hull. Shooting through the foam seriously hampers performance. In such cases, another type of transducer -- such as a transom-mount -- is more practical. There are a number of methods for securing a shoot-thru style transducer. Some can be bolted on. Some are designed to be fiberglassed or epoxied into place. Still others require a special interior enclosure that completely encapsulates the transducer in fluid such as castor oil. We can help you decide on the installation method that best suits your needs!

SPEED & TEMPERATURE SENSORS All Furuno echo sounders will display boat speed and surface water temperature, when connected with the proper sensors. In fact, some Furuno transducers -- ones known as "multi-sensors" -- have built-in speed and temperature sensors. Most transducers, however, handle only echo sounding/fish-finding. To read boat speed and water temperature, a separate sensor is required. These sensors come in two styles: transom mount and thru-hull (shown here). Like transom mount transducers, transom mount speed/temperature sensors mount at the bottom of the transom. They should be mounted just low enough to allow water flowing off the bottom of the boat to turn a speed-sensing paddle wheel. As with thru-hull transducers, thru-hull speed/temperature sensors require cutting a hole in the bottom of the boat, as shown. These sensors do not need to mounted on a horizontal plane. They can be installed on a dead-rise angle without a fairing block.

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