NMEA 0183 vs NMEA 2000 for Autopilots

What NMEA 0183 and NMEA 2000 are

NMEA 0183 and NMEA 2000 are two ways marine electronics exchange data. NMEA 0183 is the older serial interface that sends data in sentences from one talker to one or more listeners. NMEA 2000 is a modern CAN-based network standard that lets multiple devices share data on a single backbone.

The National Marine Electronics Association describes NMEA 2000 as a low-cost, moderate capacity, bi-directional, multi-transmitter/multi-receiver instrument network that is self-configuring and has no central controller. That means you can plug an autopilot, a chartplotter, a wind sensor, and a GPS receiver into the same network, and they all talk to each other.

For a buyer, the practical difference is wiring and flexibility. NMEA 0183 requires a dedicated wire pair for each data stream, and you often need to decide which device is the talker and which is the listener. NMEA 2000 uses a backbone cable with drop cables, so adding a device is as simple as connecting it to the network.

How autopilots use these networks

An autopilot needs a heading reference. Many modern autopilots take that heading from a dedicated compass sensor on the network, or from a heading source like the Furuno NavPilot 300, which requires a compatible NMEA 2000 heading source when used without a rudder feedback unit. The autopilot also can receive GPS data for route following and wind data for wind mode, if those instruments are also on the network.

On NMEA 2000, data travels as Parameter Group Numbers, or PGNs. On NMEA 0183, data is sent as sentences. The key difference is how many devices can listen: a NMEA 0183 talker typically has one listener or a daisy chain, while NMEA 2000 is a bus with many listeners.

If you are comparing autopilots, you will see that many complete packs include a control head and a heading sensor. The control head is your interface to the network, and the heading sensor feeds the autopilot. You can read more about control head options in the guide to autopilot control heads.

• Many autopilots support NMEA 2000 as their primary network connection.
• Legacy NMEA 0183 autopilots need separate wires for each data source.
• Some autopilots have a built-in heading sensor and do not need a network to steer.

Why NMEA 2000 is better for sensor sharing

For sensor sharing, NMEA 2000 is the better choice. Because it is a multi-transmitter, multi-receiver network, any device can listen to any other device's data without extra wiring. The network is self-configuring, so you do not need to set up talker and listener addresses. Adding a sensor is a matter of connecting it to the backbone.

NMEA 0183 requires you to wire each talker to each listener. If you want the autopilot to see GPS and wind, you need separate wires and sometimes a multiplexer. In a modern boat with many instruments, NMEA 2000 reduces cabling and makes it easier to expand the system later.

For example, if you have a chartplotter that sends route data, an autopilot on NMEA 2000 can follow that route directly. On NMEA 0183, you would need to connect the chartplotter's output to the autopilot's input with a specific wire, and you might need a converter if the chartplotter only outputs NMEA 2000.

When NMEA 0183 still appears

NMEA 0183 is still present on older autopilots and on some budget models. If your boat already has NMEA 0183 instruments, you may want an autopilot that accepts that protocol. But for a new installation, check whether the autopilot supports NMEA 2000. Many current autopilot packs, like Raymarine's Evolution series, are designed to be part of a network, although the specific protocol support is not stated on every pack page.

If you are replacing an old autopilot, you might be able to keep the existing drive and just replace the control head and sensor. That is where a core pack comes in. A core pack usually includes the control head and sensor but not the drive. You can see which core packs are available in the guide to autopilot core packs.

On the other hand, if you are starting from scratch, a complete pack includes the drive, control head, and sensor. That is often the simplest way to get a networked autopilot. Compare complete packs in the guide to complete autopilot packs.

What to search for on an autopilot listing

When you read an autopilot listing, look for 'NMEA 2000' or 'NMEA 0183' in the title or bullet list. Some listings say 'N2K' for NMEA 2000. If the listing does not mention networking, ask the seller or consult the maker's manual. The autopilot may have its own heading sensor and still work alone, but if you want it to talk to your chartplotter or share sensor data, you need to know which network it uses.

The control head choice is part of the network. You can read about control head options in the guide to autopilot control heads.

Also note whether the listing mentions a proprietary network name like SeaTalk or SimNet. These are often names for NMEA 2000-compatible networks, but you should confirm with the maker. The listing may also say 'compatible with' a certain chartplotter brand, but that does not guarantee NMEA 2000 support.

• Look for 'NMEA 2000' in the title or description.
• Note whether the listing says 'SeaTalk' or 'SimNet'; those are often proprietary names for NMEA 2000-compatible networks, but confirm with the maker.
• Check if the pack includes a heading sensor that can feed the autopilot without a network.
• If the listing says 'no drive' or 'core pack', you will need to supply your own drive unit.

Questions to ask before you buy

Before you buy, ask the seller or dealer: Does the autopilot connect to NMEA 2000? Does it accept NMEA 0183? Does it need a separate heading sensor, or is one built in? Can it receive route data from my chartplotter? These questions help you understand what network cables and sensors you may need.

The maker's manual is the final authority. If you are replacing an autopilot, keep the existing network in mind. If you are adding an autopilot to a boat with a modern chartplotter, NMEA 2000 will likely be the network you want to use.

For a sailboat, you may also want wind data for wind mode. That requires a wind sensor on the same network. For a powerboat, you might want GPS data for route following. Both are easier on NMEA 2000. You can explore the differences between sail and power autopilots in the sailboat autopilot guide and the powerboat autopilot guide.

What to pick for your situation

Questions

Can an autopilot work without NMEA 2000?

Yes. An autopilot can be a standalone unit with its own heading sensor and no network connection. But it will not share data with a chartplotter or other instruments, so route following and wind mode may not be available.

Do all autopilots support NMEA 2000?

No. Some older or basic autopilots use NMEA 0183 only. Check the listing for the network type before buying.

What does 'N2K' mean?

N2K is a shorthand for NMEA 2000. You will see it on some listings.

Can I convert NMEA 0183 to NMEA 2000?

There are gateways that bridge the two, but not every autopilot supports both. If you need a converter, verify that the autopilot accepts the converted data.

Does an autopilot need a specific heading sensor on the network?

Some autopilots, like the Furuno NavPilot 300, require a heading source on NMEA 2000 if no rudder feedback unit is used. The maker's manual will state the requirement.