How to Install a Transducer

through hull transducer In Hull Transducer transom transducer

Getting a crisp image on your fishfinder is closely linked to the quality of your transducer. It is your transducer that sends information about what happens underneath the water to your fishfinder. If you want to get the best out of your fishfinder, the transducer has to be perfectly installed. With the increasing number of installation tools available on the market, it is important to dwell a bit on some basic rules before you take the plunge.

Installation of a simple transducer

The location and the installation of a transducer connected with a fishfinder or a combo gps / fishfinder will have an impact on the quality of the signals sent to the echo sounder:

- The transducer must always sit below the waterline,

- The transducer has to be at a distance from the propeller to avoid wash and bubbles that could compromise the information sent to the unit,

- It should be mounted 1.5 cm below the extended waterline of the boat, with a slight angle to prevent air bubbles from forming,

transducer positioning

- The echo sounder, just like any piece of marine electronics, should be connected directly to the battery. The propulsion system of your boat will determine the kind of transducer you’ll be using as well as its location on the boat. But there are some basic rules:

- The transducer has to sit near the hull centreline, separate from turbulence,

- Not too close to the bow to protect the transducer from waves,

- It also has to be located in front of the propeller to keep it away from turbulence and bubbles,

- If you’re left with some slack after you route the cable, do not roll it up as this may interfere with the quality of the information that is sent to the echo sounder.

Types of transducers and installation

- Outboard: transom-mount transducer. Has to be mounted on the right hand side of the transom where it will be best protected from wash (example of transom-mount transducer: Humminbird SH-A03T).

humminbird sh-a03t

On an outboard, the transom-mount transducer should be installed on the right hand side of the transom to keep it away from the prop.

Inboard shaft line : though-hull or in-hull (Example: Airmar P79 600W in-hull transducer)

Airmar P79

- Inboard Z Drive (cola) : through-hull (Example: Lowrance LSS-2)

lowrance lss 2

- Sailboat : through-hull or in-hull, 40 cm in front of the keel (Example: Humminbird SH-B03 FM in-hull transducer).

Humminbird SH-B03FM

Transducer location on inboards and outboards

transducer position

Near the centreline, in front of the engine


In-hull transducer

in hull transducer position

1 : Use some epoxy or araldite two-part adhesive. Do not allow air bubbles to form during the process.

2 : The hull must be less than 15 mm thick

Through-hull transducer, V keel

position sonde traversante fond avec V

1 : Bilge

2 : Hull

3 : Bilge

4 : Transducer must be parallel with water surface

On outboards


The transom-mount transducer has to be mounted on the right-hand side of the transom to avoid turbulence caused by the propeller.


Obviously, you will have to adapt the installation to the specific requirements of your boat.

For instance, you can fit a wooden boat with a bronze through-hull transducer (never mount a bronze transducer on an aluminium craft!) while you want to get a plastic through-hull transducer if your boat hull is made from polyester.

Important : whatever the option and the kind of transducer you choose, the transducer should always sit at a right angle to the waterline, unless it is a through-hull transducer.

How to install an in-hull transducer on a transom

If you don’t want to cut a hole in your boat hull, you can mount your transducer inside the hull so that it can shoot through it. Most of the time, some epoxy or araldite will do the trick, but you can also use some Sikaflex. Just be careful not to let any bubbles form while you do that. In-hull mounting is only an option for hulls that are less than 15 mm thick. Besides, the hull must be made from quality resin without any bubble, which is not the case for many boats unfortunately. Finally, make sure the surface on which you want to install the transducer is totally smooth.

fishfinder positionning boat