Transducer Placement On V-Hull Boats: Where To Mount?

The placement of a transducer on a V-hulled boat is important for getting the best reading. There are three types of transducers: bronze, plastic, and stainless steel. The type of transducer is determined by the hull construction and length. For a V-hulled boat, a thru-hull transducer is best. This type of transducer should be installed parallel to the water's surface and should have a maximum tilt of 5-10 degrees. When installing a transducer, it is important to avoid areas with currents that could distort the measuring results, such as thru-hull fittings, drain holes, and outboard sea valves. It is also important to consider the boat's trailer rollers or lifting points when mounting a thru-hull transducer.

Transducer installation methods

Transom Mount Transducers

Transom mount transducers are typically installed on the transom of the boat, slightly lower than the hull. It is important to use a straight edge to locate the transducer and fix the mounts so that the screws are midway in the slots. Look for an area of minimal turbulence when underway, and avoid mounting behind planing strakes or scuppers.

Thru-Hull Transducers

Thru-hull transducers require drilling a hole in the hull, and they are often used for fiberglass boats. It is important to select the correct transducer material (bronze, plastic, or stainless steel) that is compatible with the hull material. The installation process involves bedding the transducer with marine sealant and ensuring it is securely fastened to the hull. Thru-hull transducers can also be mounted using a fairing block to improve high-speed operation.

In-Hull Transducers

In-hull transducers are mounted on the inside of the hull and transmit sonar signals through fiberglass. This method eliminates the need for drilling holes in the hull. However, it requires a solid fiberglass surface and does not include a sea-temp or speed sensor. The installation process involves choosing the right location, testing and adjusting the transducer, measuring and adjusting for the deadrise angle, and bonding the housing to the hull.

Pod and Pocket/Keel Transducers

Pod transducers are designed for trolling motors and are attached via a clamp assembly. Pocket or keel transducers, on the other hand, are typically used on commercial vessels and are mounted flush with the hull or directly in the keel.

Transducer positioning

Transom Mount Transducers

When mounting a transom transducer, use a straight edge to locate the transducer so that it sits slightly lower than the hull. Fix the mounts so that the screws are midway in the slots. Look for an area of least turbulence when underway. Do not mount behind any planing strakes or scuppers that may be on your hull.

Thru-Hull Transducers

Thru-hull transducers are enhanced by the use of a fairing block. This keeps the transducer face parallel with the sea floor and improves high-speed operation by creating a smooth water flow around the transducer. These transducers generally give better readings at speed and in a following sea.

A thru-hull transducer with a tilted element can be flush-mounted on a deep V-hull without the need for a fairing block. The tilt element allows the internal ceramic to be tilted for flush mounting.

When installing a thru-hull transducer, the keel arrow needs to point at the keel and not in the direction that the keel runs. Also, be aware of hull openings or projections in front of the mounting location—it's very difficult to move a thru-hull transducer once it has been fitted.

In-Hull Transducers

In-hull transducers should be contained in a tank cut to match the deadrise of the vessel and filled with propylene glycol (marine antifreeze). The tanks should then be bonded to the hull using fibreglass resin.

In-hull transducers must be fitted before fixing the tank. To find the best place to put it, you can use one of three methods:

• Flood the bilge area
• Put the transducer into a bag and fill it with water
• Use a water-based lubricant to temporarily 'stick' the transducer in place

Pod Transducers

Pod transducers are designed to be fitted to trolling motors and attach via a large clamp assembly to the motor housing. It is important that enough free cable is left at the top of the motor to ensure it can turn freely.

Pocket or Keel Transducers

Pocket or keel transducers are usually only used on commercial vessels. They have a housing that is designed to flush mount in an external hull blister or directly in the keel. They are typically mounted towards the front of the boat around the second bow wave.

General Mounting Advice

• Mount on the starboard side of the vessel if the prop is clockwise-turning (95%)—this means that water is flowing over the top of the transducer.
• Never mount inline with a hull projection like a water intake.
• Have a small amount of kickdown on the transducer, around 2-5 degrees is good. This ensures a clean flow of water hits the transducer face.
• Before mounting, take the boat for a run and look for a smooth flow area at the transom of the boat.
• Remember to account for trailer rollers or lifting points when mounting thru-hull transducers.
• For stepped hulls, the transducer needs to be mounted on the first step and have enough room to kick up if struck.
• Adjust the transducer so that it has around a 3-5-degree tail-low tilt.

Transducer testing

Testing the Transducer:

• Connect the transducer to the fish finder or sonar unit.
• Hang the transducer overboard while the boat is floating in at least 25 feet of water.
• Observe the bottom return and establish a performance baseline.
• Place the transducer inside a thin plastic bag partially filled with water and seal it with a cable tie.
• Wet the mounting surface on the hull.
• Press the active face of the transducer against the hull at the intended installation location.
• Compare the bottom return to the baseline. If the reading is similar, the transducer is functioning properly and the mounting location is suitable. If the reading differs, you may need to find another location and repeat the test.

Additional Tips:

• Ensure there are no external strakes, intakes, or other hull features that could cause aerated water to flow over the transducer's location.
• The transducer should be located as close to the centerline as possible.
• If the mounting surface is not smooth, use a disc sander to grind it flat.
• To prevent overheating, mount the transducer in a cool, well-ventilated area away from inboard engines or other heat sources.
• Before final installation, lightly sand and clean the mounting surface with isopropyl alcohol to ensure it is free of any wax, paint, oil, or moisture.

Alternative Testing Methods:

If you are unable to test the transducer in the water, there are a few alternative methods you can try:

• Using a Length of Pipe: Obtain a 2-3 foot length of PVC pipe and cap one end. Fill the pipe with water or antifreeze and hold it tightly over the transducer. The reading should be about 4-5 times the length of the pipe.
• Using a Bucket of Water: Connect the transducer to a power supply and lower it into a bucket of water. This will allow you to observe the echoes and determine if the transducer is functioning properly.
• Feeling the Pulses: With the system switched on, apply light fingertip pressure to the face of the transducer. You should be able to feel the pulses or hear the ticking sound, indicating that the transducer is working.

Hull construction

The type of transducer you can install on your V-hull boat depends on the hull construction. The three types of transducers available are bronze, plastic, and stainless steel. Bronze transducers are recommended for fiberglass or wooden hulls. Plastic transducers are recommended for fiberglass or metal hulls. Stainless steel transducers are recommended for steel or aluminum hulls.

If you have a fiberglass or wooden hull, you can choose either a bronze or plastic transducer. If you have a metal hull, a plastic transducer is recommended. For steel or aluminum hulls, a stainless steel transducer is the best option.

It's important to note that plastic transducers are not suitable for wooden hulls, as the expansion of the wood can damage the plastic. Additionally, if you have a cored fiberglass hull, you will need to make special modifications for an in-hull transducer to function properly.

When installing a transducer on a V-hull boat, it's crucial to follow the manufacturer's instructions and take the necessary precautions to ensure a secure and proper installation.

Transducer maintenance

Transducers are electrical sensor devices that measure depth and water temperature, feeding this information into a fish finder. They are hidden below the waterline and are essential for navigation and fishing.

Placement and Installation:

When installing a transducer, it is crucial to select the correct location and follow the proper installation procedure. Ensure that the transducer is placed in an area with smooth water flow, free from turbulence, air bubbles, and obstructions. The transducer must remain continuously immersed in water, with its beam unobstructed. Choose a location away from interferences, such as the propeller, machinery, and other cables, to minimise background noise.

Cleaning and Maintenance:

The primary maintenance task is to keep the face of the transducer free from any buildup that may hinder its performance. This includes removing dirt, marine plant life, and barnacles, which can cause turbulence and trap air, affecting the transmission and reception of signals. Clean the transducer as soon as possible after hauling the boat to prevent contaminants from drying and becoming more difficult to remove. Use a flat tool, such as a putty knife, to carefully remove any buildup, and finish by wet-sanding with fine-grit sandpaper.

It is important to note that scratches or nicks on the transducer face can also cause turbulence and trap air, impacting its performance over time. The outer layer of the transducer face is usually made of polymer or epoxy, so light wet-sanding can remove minor scratches.

Avoid applying anti-fouling coatings to the transducer, as these can be harmful and cause issues. Instead, consider using a diver to clean the transducer or wait until the boat is out of the water for maintenance.

Sealant Inspection:

For through-hull transducers, inspect the sealing provisions every time the boat is removed from the water. Look for dried-out, missing, or cracked sealant, which may indicate movement or damage. If any issues are found, remove the old sealant, take out the transducer, and re-bed it into the hull. This may be a challenging task best left to a professional.

Wiring and Connections:

Regularly inspect the wiring and electrical connections of the transducer system. Ensure that connections are secure and free from corrosion. Check the condition of the transducer cable, as nicks or breaks in the sheathing can allow electrical noise or interference from other devices to impact the performance of the fish finder. Keep transducer cables separate from cables of VHF radios, inverters, and other potential sources of electrical interference to minimise signal disruption.

By following these maintenance steps, you can ensure the optimal performance of your transducer and avoid issues with your boat's navigation and fishing capabilities.

Frequently asked questions