Autopilot Interface: Connecting to Other Instruments

What is NMEA 2000 and why it matters

NMEA 2000 is a standard for connecting marine electronics on a boat. It is based on CAN (Controller Area Network) communications, which allows multiple devices to talk to each other over a single cable. The National Marine Electronics Association (NMEA) describes it as a low-cost, moderate-capacity, bi-directional network that is multi-master and self-configuring, with no central controller. This means your autopilot, GPS, wind sensor, and chartplotter can share data like heading, position, and wind speed without needing separate wires for each connection. For a deeper look at how this network works, see our article on NMEA 2000 connectivity.

For an autopilot, NMEA 2000 is the common way to receive information from other instruments. For example, a GPS can send your boat's position and course over the network, and the autopilot can use that to steer a route. A wind sensor can send apparent wind angle and speed, which a sailboat autopilot can use to hold a wind angle. A chartplotter can send route data, allowing the autopilot to follow a path. Understanding this network helps you choose an autopilot that will work with the instruments you already have or plan to add.

• NMEA 2000 is a standard for interconnecting marine electronics.
• It uses a single cable to share data between multiple devices.
• The network is self-configuring, so devices can be added or removed easily.
• Autopilots use NMEA 2000 to receive data from GPS, wind sensors, and chartplotters.

Proprietary networks: SeaTalkng and others

Some manufacturers use their own network names on listings. Raymarine, for example, uses SeaTalkng for its Evolution autopilot systems. SeaTalkng is designed to work with NMEA 2000, so you can connect Raymarine autopilots to other NMEA 2000 devices. Other brands like Simrad and B&G use SimNet, which is also NMEA 2000 compatible. These proprietary names often appear in product titles, but they generally mean the device can connect to a standard NMEA 2000 network, possibly with an adapter. If you are comparing brands, our Raymarine autopilot guide explains the differences in their systems.

When you see a listing that mentions SeaTalkng or SimNet, it is a signal that the autopilot is designed to integrate with that brand's ecosystem. However, because these networks are based on NMEA 2000, they can typically connect to other NMEA 2000 devices. The key is to check the product's specifications or the maker's page to confirm compatibility. For example, Raymarine's autopilot packs are described as part of the Evolution series, which uses SeaTalkng for networking.

If you have an older boat with NMEA 0183 instruments, you may need a gateway to convert between NMEA 0183 and NMEA 2000. This is a separate device that allows data to flow between the two standards. Not all autopilots support NMEA 0183 directly, so a gateway is often the solution for integrating older instruments.

• SeaTalkng is Raymarine's network, compatible with NMEA 2000.
• SimNet is used by Simrad and B&G, also NMEA 2000 based.
• Proprietary networks often appear in product titles as a brand signal.
• Gateways can connect NMEA 0183 instruments to NMEA 2000 networks.

Connecting to GPS and chartplotters

A GPS or chartplotter provides position and course data that an autopilot can use for route following. On a NMEA 2000 network, the GPS sends its data as standard messages, and the autopilot listens for them. This allows the autopilot to steer to waypoints or follow a route created on the chartplotter. Many autopilots also have a built-in heading sensor, but the GPS can provide additional data like speed over ground. If you are adding an autopilot to a boat with an existing chartplotter, our guide to autopilots with control heads can help you choose a head that displays navigation data.

When choosing an autopilot, consider whether your chartplotter is NMEA 2000 compatible. Most modern chartplotters are, but older models may use NMEA 0183. If your chartplotter is NMEA 2000, you can connect it directly to the same network as the autopilot. If it is NMEA 0183, you may need a gateway. The autopilot's control head often displays navigation data from the GPS, so you can see your course and cross-track error.

Some autopilots, like Furuno's NavPilot 300, are designed to work with specific chartplotter lines, such as NavNet TZtouch. The maker's page notes that NavPilot is designed to match NavNet TZtouchXL, TZtouchE, TZMAP, and other navigation equipment. This indicates a level of integration, but it does not guarantee compatibility with all models. Always check the maker's specifications for your specific chartplotter.

• GPS data on NMEA 2000 includes position, course, and speed over ground.
• Chartplotters can send routes and waypoints to the autopilot.
• Older chartplotters may need a gateway to connect to NMEA 2000.
• Some autopilots are designed to integrate with specific chartplotter brands.

Connecting to wind sensors

For sailboats, wind data is crucial for sailing modes. A wind sensor measures apparent wind angle and speed, which the autopilot uses to hold a wind angle or tack. On a NMEA 2000 network, the wind sensor sends this data, and the autopilot can use it to adjust the helm. This is especially useful for cruising sailors who want to maintain a consistent wind angle without constant manual adjustments. If you are equipping a sailboat, our sailboat autopilot guide highlights models that support wind modes.

When buying an autopilot for a sailboat, check that it supports wind data over NMEA 2000. Most modern autopilots do, but some may require a separate wind sensor or a specific control head. For example, Raymarine's EV-200 Sail Pilot is designed for sailboats and works with wind instruments. The control head, like the p70s, can display wind data and allow you to select wind modes.

If your boat already has a wind sensor, verify that it is NMEA 2000 compatible. If it is an older analog sensor, you may need a converter to send the data to the network. The autopilot's manual will specify what data it can use and how to configure it. This is a question to ask your dealer or installer if you are unsure.

• Wind sensors provide apparent wind angle and speed over NMEA 2000.
• Sailboat autopilots use wind data for wind angle sailing modes.
• Check that your wind sensor is NMEA 2000 compatible.
• Older sensors may need a converter to send data to the network.

Network cables and backbone basics

A NMEA 2000 network uses a backbone cable with drop cables connecting each device. The backbone is the main trunk, and each device connects to it with a drop cable. This allows multiple devices to share data without a central hub. The network is powered by a single power source, usually connected to the backbone. The NMEA 2000 standard describes this as a multi-transmitter, multi-receiver network, meaning any device can send and receive data. For a visual explanation, see our article on the NMEA 2000 backbone.

When planning an autopilot installation, you need to consider where the backbone will run and how many devices you will connect. Each device needs a drop cable, and the backbone must be terminated at both ends with terminators. This is part of the installation process, which is best left to a qualified installer or done according to the maker's manual. The autopilot pack may include some cables, but you may need additional ones for your specific setup.

The length of the backbone and drop cables can affect the network's performance, but the NMEA 2000 standard is designed for moderate capacity. For most recreational boats, a simple backbone with a few devices works well. If you have many devices, you may need to plan the network layout carefully. This is a question for your installer or the maker's documentation.

• A NMEA 2000 network has a backbone cable and drop cables for each device.
• The network is powered by a single source connected to the backbone.
• Terminators are required at both ends of the backbone.
• Installation should follow the maker's manual or be done by a qualified installer.

What to check on a listing

When reading an autopilot listing, look for mentions of NMEA 2000, SeaTalkng, or other network compatibility. The title may say 'NMEA 2000' or 'SeaTalkng' to indicate the interface. The bullet list may specify which data the autopilot can receive, such as GPS, wind, or route data. If a listing does not mention a network, it may still be compatible, but you should check the maker's page for details. Our complete autopilot packs guide shows how various listings are structured.

Also check whether the control head is included and what it displays. Some control heads can show navigation data from the GPS, wind data, or autopilot status. The control head is your interface to the network, so it should be able to display the information you need. For example, Raymarine's p70s control head is designed for sailboats and can show wind data.

Finally, consider the drive unit. The autopilot's drive connects to your steering system, but the network interface is separate. The drive does not affect how the autopilot connects to other instruments, but it determines how the autopilot steers the boat. Make sure the drive matches your steering type.

• Look for 'NMEA 2000' or 'SeaTalkng' in the title or bullets.
• Check if the control head displays GPS, wind, or route data.
• Verify compatibility with your existing instruments on the maker's page.
• The drive unit is separate from the network interface.

Questions to ask the seller or dealer

Before buying, ask the seller or dealer about network compatibility. Questions like: 'Does this autopilot connect to my chartplotter via NMEA 2000?' or 'What data can it receive from my wind sensor?' are important. The seller should be able to confirm compatibility or point you to the maker's specifications. If they cannot, check the maker's page directly. Our marine autopilot buying guide includes a checklist of questions to ask.

You should also ask about the installation. Who will install the autopilot and the network? A qualified installer can ensure the network is set up correctly, with proper termination and power. The maker's manual will have details, but an installer can handle the specifics. This is especially important if you are adding the autopilot to an existing network with other devices.

Finally, ask about the control head. Does it show the data you need? Can you customize the display? Some control heads allow you to select which data fields to show, such as wind angle, course, or cross-track error. This can make the autopilot easier to use, so it is worth asking about.

• Ask about NMEA 2000 compatibility with your existing instruments.
• Inquire about installation and who will set up the network.
• Check if the control head displays the data you need.
• Confirm that the maker's page supports the compatibility claims.

What to pick for your situation

Questions

What is NMEA 2000?

NMEA 2000 is a standard for connecting marine electronics on a boat. It uses a CAN-based network to allow devices like autopilots, GPS, and wind sensors to share data over a single cable. It is multi-master and self-configuring, so devices can be added or removed easily. For more details, see our NMEA 2000 connectivity article.

Can a Raymarine autopilot connect to a Garmin chartplotter?

Raymarine autopilots use SeaTalkng, which is compatible with NMEA 2000. If your Garmin chartplotter is NMEA 2000 certified, it can connect to the same network, and the autopilot can receive data from it. Check the maker's specifications for compatibility. Our Raymarine autopilot guide covers common integration questions.

Do I need a separate heading sensor if I have a GPS?

Most autopilots include a heading sensor, like a compass or gyro, which is essential for steering. A GPS provides position and course, but not the fast, accurate heading needed for autopilot control. The heading sensor is a separate component, often built into the autopilot's sensor unit. This is explained in our autopilot sensor requirements article.

What is a gateway and when do I need one?

A gateway converts data between different network standards, such as NMEA 0183 and NMEA 2000. You need one if you have older instruments that use NMEA 0183 and want to connect them to a NMEA 2000 autopilot network. The gateway allows data to flow between the two systems.

Can I connect my autopilot to a wind sensor?

Yes, if your wind sensor is NMEA 2000 compatible and your autopilot supports wind data. Sailboat autopilots often have modes that use wind angle for steering. Check the autopilot's specifications to confirm it can receive wind data over the network.

What should I do if my instruments are not NMEA 2000?

If your instruments use NMEA 0183, you can use a gateway to connect them to a NMEA 2000 network. Alternatively, you may need to upgrade your instruments. Consult with a dealer or installer to determine the best solution for your boat.