Before buying hardware or starting installation, it is wise to first do a complete review of your vessel’s electrical system, navigation system, and available space for new equipment. Older boats, especially, often have very customized layouts and may not have wiring or mounting points suitable for modern AIS.
The installation location must be dry and secure but near the main navigation station with good ventilation and relatively easy access for cables. Take measurements of the available space to be sure the AIS model you select will fit without interfering with other equipment.
Evaluate your power source. AIS units operate on 12 or 24 V DC. It is important to ensure that your vessel’s battery system can accommodate the additional load. Older boats may have weak alternators or batteries, and you could be required to upgrade to consistently support AIS.
You should also assess the existing antenna capability. AIS uses very high frequency (VHF) antennas. Some vessels may require a dedicated antenna, or an antenna splitter may be needed to allow sharing with a marine radio. The use of a high-quality antenna in the correct location greatly influences the performance and reliability of AIS.
Consider the possibility of integration. Many modern AIS units interface with chartplotters, radar, or multifunction displays. Knowing what navigation technology is on board helps in choosing a compatible AIS device that guarantees seamless data sharing.
Choosing the Right AIS Equipment for Older Vessels
There are two types of transceivers. Class A units offer higher power and more frequent transmissions, typically used on commercial ships. Class B devices work well for recreational and smaller vessels, balancing functionality with affordability.
For older boats, a Class B AIS transceiver is more suitable. These are compact, easier to install, and less expensive, but still provide accurate tracking and identification capabilities.
Pay attention to whether you want a standalone AIS unit or one integrated with your existing navigation system. Standalone devices function independently and usually connect via NMEA (National Marine Electronics Association) protocols to display data on compatible screens. Integrated units simplify cabling and display but might limit flexibility if your navigation system is outdated.
Some AIS transceivers have built-in GPS receivers, while others rely on external GPS antennas or feed from your existing GPS system. Installing a GPS antenna might add complexity to the setup but often improves accuracy.
Although existing VHF antennas will do the job, in some cases, better signal transmission and reception will be achieved by installing a dedicated AIS antenna. Many experts advise mounting the AIS antenna at the greatest height available and ensuring it’s positioned away from other antennas to prevent interference.
Make sure the AIS unit you choose is marine-certified and compliant. Global regulations, including IMO type approval, guarantee that the equipment complies with essential performance and emission requirements.
Step-by-Step Installation
The AIS transceiver shall be mounted in a dry, accessible location near the helm station. Use the correct brackets or mounting hardware to provide a vibration-free installation. Do not install the unit near engines or electrical motors, which may cause interference.
Power the AIS unit from your boat’s main power source, usually the DC electrical panel or directly from the batteries with a fuse or circuit breaker in line. Prevent resets or malfunctions by providing clean, stable power.
Install the AIS antenna as per the manufacturer’s instructions. Run the coaxial cable to the AIS unit, taking care to use proper cable types and weather-resistant connectors. If sharing an antenna with your VHF radio, install a splitter appropriately.
Connect the built-in or external GPS antenna. Position the GPS antenna in an open area where it has an unobstructed view of the sky. Run cabling securely to avoid water ingress and interference.
Link your AIS unit to your chartplotter or multifunction displays using NMEA 0183 or 2000 protocols. Proper configuration on both the AIS device and navigation equipment ensures real-time sharing of AIS targets and information.
Power up the system and ensure that the AIS is transmitting your vessel’s information correctly, which includes GPS position and ship identity. Also, verify that nearby AIS signals are clearly received. If necessary, reposition antennas and adjust settings.
Protect all connections against moisture using marine-grade sealants and cable glands. Prevent cable wear caused by vibration or movement by securing loose cables with clamps or ties.
Don’t rush the installation. Properly routing cables, securing fittings, and testing each component will prevent problems down the road and ensure reliable performance for the long term.
Troubleshooting Common AIS Retrofit Challenges on Older Vessels
In older boats, voltage drops or interference may be caused by aging batteries, undersized wiring, or overloaded alternators. If the AIS unit keeps rebooting or losing signal, double-check the power source quality and try isolating the AIS circuit on its own fuse.
AIS VHF frequencies are susceptible to electrical noise generated by engines, alternators, or other electronics on board. Problems include noisy reception or limited transmission range. Adding ferrite chokes on wiring, repositioning antennas, or upgrading to shielded cables typically resolves these disturbances.
Too close to metal objects, masts, or antennas for other radios reduces AIS range and clarity. Experimenting with antenna height and clearance around the antenna often yields big improvements.
Compatibility between AIS units and older chartplotters may require software updates or configuration tweaks. Ensure devices use the correct NMEA versions and baud rates. If an older display can’t integrate AIS data, consider adding a dedicated AIS display or upgrading your navigation system.
Older vessels may lack quality GPS antennas or have obstructed views from tall structures. Upgrading to an external GPS antenna with good sky visibility is a simple solution.
Benefits of Retrofitting AIS on Older Vessels
By transmitting your own position and receiving positions from other ships, you can see more clearly in the vicinity—even in darkness, fog or congested shipping lanes.
The AIS system further supports safety messaging and distress alerting. In situations of emergency, you are able to rapidly inform ships nearby as well as rescue authorities.
Knowing the vessel traffic and optimizing the sail or cruise path accordingly with AIS data helps avoid unnecessary course deviations and waiting time. This leads to a saving of fuel and time.
Having AIS on board may enhance the resale value of your vessel. Prospective buyers appear to be drawn to boats equipped with state-of-the-art safety and navigation equipment.
For the commercial sailor, retrofitting AIS opens up chances for attaining shipping certifications and allows one to venture into wider operational areas that have no restrictions.