A sonar transducer forms the link between your Simrad display or sonar module and the water.
Transducers act as both a powerful speaker and a sensitive microphone, transmitting sonar signals into the water and listening for echoes returned from the bottom and other submerged targets.
Most transducers must be exposed directly to the water in order to function; common installations involve mounting through a hole drilled in your hull, transom-mounting below the waterline, or external mounting in a specially designed keel or hull pocket. Alternatively, solid fiberglass hulls permit the use of in-hull tank mounted or ‘shoot-thru-hull’ transducers, which are mounted on the inside surface of the hull and fire a sonar signal straight through to the water below.
Your boat’s hull type will determine the transducer mounting styles available to choose from. Selecting the right style then means finding your ideal balance between transducer performance, vessel performance, installation cost and complexity.
Thru-Hull Tilted Element
These transducers mount through a hole drilled in any fiberglass, metal or wooden hull, with the outside of the fitting flush against the exterior hull surface. Inside the fitting, the transducer’s active elements are permanently tilted to match your hull’s deadrise, ensuring the sonar beam is aimed straight down.
The flush-mount design of these transducers allows for smooth water flow over the hull, meaning less drag and minimal effect on boating performance. However, tilted-element transducers may be susceptible to performance loss due to external factors.
Thru-Hull with Fairing
These common transducers are mounted on a stem that passes through a hole drilled in any fiberglass, metal or wooden hull. The transducer protrudes beyond the hull surface, secured inside a fairing block cut to adjust for hull deadrise while allowing the smoothest possible water flow.
Thru-hull transducers with a fairing block tend to offer the most reliable and accurate sonar performance. However, drag caused by the protruding transducer can negatively affect boat speed and fuel efficiency.
Stainless steel transducers are recommended for metal hulls, and bronze transducers for wooden hulls; either type may be installed in a fiberglass hull.
Transom mount transducers are affixed to the stern of your vessel, where smooth water flow is passing off the transom. This mounting style offers the simplest installation and maintenance, without requiring any holes to be drilled beneath the waterline. Installed on a bracket, the transducer can be easily adjusted to compensate for transom angle; many brackets also allow the transducer to be folded up and out of the way for safe trailering.
Designed for smaller outboard and inboard/outboard boats, these transducers are well suited to planing hulls. Installed in the proper location, transom-mounted transducers can offer high reliability with minimal effect on vessel performance.
Chest mount transducers are installed inside a small box attached to the outside of your vessel, with the active face and sides of the transducer exposed to the water. A small hole must be drilled in the hull to allow the transducer cable to enter via a stem or stuffing tube.
Most commonly used aboard offshore commercial vessels, this fully-external mounting style has the greatest impact on vessel performance and is unsuitable for high-speed powerboats.
These transducers are installed within a small custom pocket in your vessel’s hull or keel, flush to the surface. Though retrofit installation is possible, these transducers are most commonly mounted in vessels where a suitable pocket is supplied pre-cut by the boat builder.
Pocket or keel-mounted transducers provide reliable and accurate sonar performance, with some impact to boat speed and fuel efficiency. As a common alternative, thru-hull transducers with a fairing block deliver comparable sonar performance and vessel impact.
In-Hull Tank Mount
Only suitable for solid fiberglass hulls, in-hull or "shoot-thru-hull" transducers don’t require a hole to be drilled for installation. The transducer is mounted in a liquid-filled tank inside your vessel, bonded to the inner surface of the hull, and transmits sonar signals through the hull without direct exposure to the water. Great for trailer boats, there’s no external hardware to be damaged during trailering, launch and retrieval.
In-hull mounting means no added drag, and thus no impact to your boat’s speed or fuel efficiency. Expect reliable sonar performance at high speed, as water isn’t constantly moving over the face of the transducer. However, transmitting and receiving through the hull limits maximum sonar depth and fish-finding capabilities compared to thru-hull, transom, or other in-water installations.
Next: Read about sonar compatibility