The Airmar P79 In-Hull Transducer is a specialized depth-sensing device designed for integration into fiberglass-hulled boats. It is engineered for high-speed performance, particularly in powerboats and racing sailboats, and is intended for use in environments where acoustic noise and hull construction can impact the accuracy of sonar readings. Proper installation is critical for the transducer to function effectively and avoid damage due to improper mounting or exposure to harmful substances.
This guide compiles and organizes key technical specifications, installation procedures, and safety considerations from multiple manufacturer-provided resources, including installation manuals and user guides. The objective is to provide a step-by-step reference for U.S. consumers and DIY enthusiasts who are installing the P79 in-hull transducer on fiberglass-hulled vessels.
Installation Overview and Prerequisites
Before beginning the installation process, it is essential to review the instructions thoroughly. The manufacturer explicitly states that these installation instructions supersede any other instructions found in the instrument manual if they differ. Therefore, adhering strictly to the provided guidelines ensures compatibility and optimal performance.
The installation requires the use of various tools and materials, including a drill, hole saw, miniature disk sander, casting epoxy or resin, a paper cup and stirrer, silicone sealant (such as GE Silicone I or II), a screwdriver, a level, and a carpenter's square. Additional optional materials include a thin sealable plastic bag, twist-tie, water-based lubricant (like K-Y® jelly), and petroleum jelly.
Safety precautions are also emphasized. The use of solvents such as acetone is strongly discouraged, as they can weaken plastics and compromise the integrity of the hull. Safety goggles and a dust mask are recommended for some installation steps, particularly when sanding or working with epoxy.
Preparing the Installation Site
The P79 is designed specifically for fiberglass-hulled boats and is not suitable for other materials. The location of the transducer is crucial for both performance and durability. The fiberglass section where the transducer is mounted must be solid—without coring, flotation material, or dead air space between the inner and outer hull layers. Cored areas, which often contain balsa wood or structural foam, are poor conductors of sound and should be avoided.
The ideal installation site is one where the water flowing across the hull is smooth, with minimal turbulence and bubbles. The transducer must also be positioned away from water intake or discharge openings, as well as from strakes, fittings, or other hull irregularities that can disrupt water flow. Additionally, the transducer should be mounted so that it is level with the hull, ensuring that the centerline (yellow line) of the transducer is aligned with the ground level (black line).
Step-by-Step Installation Process
Surface Preparation
Begin by cleaning the installation site on the hull. Remove paint, dirt, and other debris. Sand the area using sandpaper to ensure a smooth surface. The transducer itself should also be sanded to improve adhesion.Drilling and Mounting
Mark and drill the necessary holes for the transducer mount. Insert screws and secure them with sealing compound. Care must be taken to align the transducer correctly within the mount to ensure it is vertical and level.Epoxy or Resin Application
Follow the manufacturer’s instructions for mixing the casting epoxy or resin. Apply the adhesive or silicone sealant generously to both the hull and the transducer. It is important to avoid trapping air beneath the material, as this can compromise the seal.Securing the Transducer
Press the transducer into place and secure it as vertically as possible. Apply a layer of adhesive approximately 1 cm thick around the transducer. Allow the adhesive to dry according to the manufacturer’s specifications.Cable Installation
Drill a hole in the hull—preferably above the waterline—for the transducer cable to enter the interior of the boat. Feed the transducer cable with the plug through the hole and seal it with sealing compound. A Scanstrut bushing may also be installed for added protection.Post-Installation Checks
After installation, ensure that the cables are routed properly, for example, through protective tubes in the keel area or along the floor. Never cut or shorten the cables unless advised by an expert. This can lead to damage or reduced quality.It is recommended to apply masking tape to the hull before applying the sealing compound. This allows excess compound to be easily removed after installation. After securing the transducer, allow the sealing compound to dry.
Immediately after launching the boat, inspect the area around the transducer for leaks. Small leaks may not be immediately visible, so it is important to recheck the condition after three hours. If any issues are found, the transducer should be removed and the installation process repeated.
Considerations for Acoustic Performance and Noise
Acoustic noise is an inevitable factor in sonar operation and can affect the quality of readings. While external noise sources such as waves, fish, and other vessels cannot be controlled, the installation location can help mitigate internal noise from the boat's propeller, shafts, and other machinery. Choosing a location that minimizes vessel-generated noise will improve the performance of the transducer and allow for a higher gain setting on the echosounder.
The P79 is optimized for high-speed use, where air bubbles and currents are less likely to disturb the transducer. At high speeds, the transducer should be positioned slightly lower than the hull's lower edge to maintain a uniform flow of water toward it. In some cases, the transducer can be mounted higher to protect it from driftwood or other debris.
Frequency and Sonar Technology
The performance of the P79 is also influenced by the sonar technology and the frequency of the transducer. Different frequencies affect the depth and clarity of the readings, and the quality of the data can vary depending on the type of sonar used. For users looking to obtain specific types of data—such as depth, speed, or water temperature—it is important to select a transducer that supports these features. Some multifunction transducers combine depth, speed, and temperature sensing into a single unit, offering a more integrated solution for boat operators.
Troubleshooting and Maintenance
If the transducer is not functioning as expected, the first step is to verify the installation. Check that the transducer is mounted in a solid section of the hull, away from coring or other material that can interfere with sound transmission. Ensure that the transducer is level and that the cables are properly routed without any damage or interference.
In the event of a leak or seal failure, the transducer should be removed and the installation process repeated. If the transducer is damaged, it should be replaced with a new unit to avoid further issues. Regular inspections are recommended, especially after prolonged use or in areas where water conditions are harsh.
Conclusion
The Airmar P79 In-Hull Transducer is a specialized device designed for high-speed and racing applications. Its installation requires careful attention to detail, particularly in selecting the correct mounting location and ensuring that the hull is solid and free of coring. By following the manufacturer’s instructions and using the appropriate tools and materials, users can ensure optimal performance and durability.
The installation process involves surface preparation, drilling and mounting, epoxy or resin application, cable routing, and post-installation checks. It is also important to consider the impact of acoustic noise and the role of frequency in sonar performance. Regular maintenance and inspections can help identify and resolve potential issues before they affect the functionality of the transducer.
For U.S. consumers, DIY enthusiasts, and IT professionals, the P79 offers a reliable and high-performance solution for depth sensing on fiberglass-hulled boats. Proper installation and maintenance are essential for achieving accurate and consistent readings, particularly in high-speed environments where water flow and hull construction can influence sonar performance.