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How to Mount a Transducer on a Fiberglass Boat in 4 Easy Steps?

Written by Anthony Roberts / Fact checked by Jonathan Larson

how to mount a transducer on a fiberglass boat

Are you eager to find out what objects lurk underneath the waves every time you pilot your boat? Leveling up your boating adventures is a cinch if you know how to mount a transducer on a fiberglass boat. Transducers for boats are fantastic tools for mapping out objects under the sea.

Some people think installing a transducer on a watercraft requires a professional. You do not have to hire experts because I will show you two ways to install this device on your boat: through the transom & through the hull; all it takes is some drilling and setting up cables.

Things You Need for this Tutorial


Installing a transducer on a boat improves your boating experience, allowing you to tackle different fish species and look for objects in the seabed. You will need a few things to mount such a device in your fiberglass boat.

1. Boat Layout

An essential aspect of mounting a boat transducer is determining the correct location. You can only do this if you know your watercraft’s structural design.

It would be best to know the precise location of the transom, ribs, struts, and other components. You will not want to drill holes where you should not.

Ideally, you will also want to check your boat’s electrical system because you will connect the transducer to your vessel’s onboard controls.

2. Good-quality Transducer for Boats

You can pick one of several boat transducer types, depending on your needs.

You can pick a transom mount with an adjustable-angle bracket for a more straightforward installation. The only downside is that this transducer is prone to the effects of turbulent water flow.

A thru-hull transducer is perfect for producing more accurate depth readings and stronger echo returns. They are suitable for boats with center consoles and a 25-degree maximum deadrise angle.

In-hull transducers are ideal for watercraft with a maximum deadrise angle of 30 degrees and high-performance boats.

A trolling motor is one of the easiest transducers to install because you only need to clamp it inside your boat’s propeller hub.

3. Mounting Tools

Depending on the transducer type you will install in your boat, you will need a power drill and drill bits for creating holes for the mounting screws or transducer housing and cables.

You will also need sandpaper for smoothing the holes’ inside surface & rubbing alcohol/mild detergent for cleaning. Screwdrivers and a marine epoxy or sealant are also a must.

Having safety glasses and a pair of work gloves is also essential, especially when drilling holes. A face mask is also necessary when applying sealants.

Steps to Mount a Transducer on a Fiberglass Boat


Step 1. Determine where you want to mount the transducer on your boat

If you want to install a fishfinder on a fiberglass boat, your transducer’s location plays a crucial role. The transducer is at the heart of any fish-finding technology. You will want the transducer to send and receive signals unimpeded.

Ideally, you will want the transducer to be as close to your boat hull’s center spine as possible. Garmin recommends placing it on the starboard side, at least 15 inches away from the propeller for boats with outboard motors.

If you have a twin-drive boat, you can place the device between the drives. For single-drive watercraft, it would be best to position the transducer away from the propeller’s path.

You should also mount the device upstream of any discharge port, water intake, struts, fittings, or strakes.

Step 2. Drill holes through the boat’s transom

Check the location of your fiberglass boat’s transom because this is the sturdiest part of your watercraft. Mark the sections where you must drill holes for the mounting screws. Get your drill with the correct size bit and drill holes through the transom.

You may also need to drill a larger hole for the cables. The cable port should always be above the waterline.

Pro Tip: Always check your transducer’s installation instructions because manufacturers can have different mounting recommendations.

Step 3. Mount the transducer

Place the transducer base plate on the surface, positioning the mounting ports over the holes on the boat. Fasten the screws to secure the base plate on your boat’s surface.

Always position the transducer parallel to the waterline to give you optimal signal transmission and reception.

If you are unsure, you might want to check your user’s manual for directions.

Step 4. Set the cables

Secure the cables to your boat’s transom before setting them through the cable hole you made. Set the wires to run through your boat and into your fishfinder console.

If it is difficult to set the cables because of obstacles in your watercraft, you might want to check the manufacturer’s recommendations to see if you can cut the wires. Ensure to connect them once set.

Here is an excellent video from Marnav Marine Electronics showing the process of installing transducer on fiberglass boat.

Steps for Mounting a Transducer Through the Hull

Step 1. Drill a hole in the boat’s hull

Similar to a transom transducer mount, a thru-hull transducer installation begins with the drilling of hole for mounting the device.

However, instead of drilling a hole on the boat’s outside surface, you will have to do it inside the hull. If the location has a rib or strut, you will have to drill from the exterior.

Pro Tip: Ensure the hole forms a 90-degree angle with the waterline. It would also help to drill counterclockwise first to avoid chipping the gel coat. Once deep enough, you can proceed to drill clockwise or forward.

Step 2. Clean the holes and the surrounding area

Wipe the hole and the surrounding area to remove any particles. Apply rubbing alcohol to aid in the cleaning process. A mild detergent also works to clean the surfaces.

Sand the hole to ensure a smooth surface, ensuring optimal sealant adhesion. Always remember to wipe off any sanding particles to ensure a smoother finish.

Step 3. Fit and secure the transducer

Apply marine sealant on the transducer gasket’s surface. Insert the transducer cables through the port before securing the device’s housing in the hole.

Press the edge of the housing against the boat’s hull to squeeze out excess marine sealant. You can opt not to wipe off the excess substrate because it can serve as an additional layer of protection against water ingress.

Fasten the housing screw on the other side of the transducer casing inside your boat. Align the arrows between the housing and the screw to ensure a correct fit.

I found an exciting video by HawkEyeElectronics showing people the complete process of through hull transducer mounting.

Pro Tip: Tighten the screw only by hand because using a wrench or pliers can damage the transducer due to overtightening.

Step 4. Connect the cable to the control console

Set the cables under your boat’s floorboard and connect them to the terminals in the fishfinder console. You might want to organize the wires and secure them with zip ties.

If you must cut wires, ensure to reconnect them accordingly. You will want to optimize your transducer’s functionality.


Leveling up your boating adventures is a breeze if you know how to mount a transducer on a fiberglass boat. Whether installed through the hull or in your boat’s transom, installing this device is easy enough for the absolute beginner.

What do you think about this tutorial? Are you more confident about mounting a transducer in your boat? If you are, other people you know might also want to gain the knowledge you now have. You can share this article with them and send me what you think in the comments below.

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