Installation · 6 minute read
NMEA 2000 autopilot integration
Plan NMEA 2000 autopilot integration: backbone layout, required data, mixed-brand limits, chartplotter control and connections to older marine networks.
An autopilot on its own network is a heading-holder. Connected properly it steers to wind, follows routes, cancels tide, warns of ships and lets you run it from the plotter at any station. The connection is or a brand variant of it, and a surprising number of pilot complaints in Australia trace back to a badly built backbone rather than the pilot.
Key facts
- Standard
- NMEA 2000; SeaTalkng and SimNet are compatible variants
- Backbone
- Two terminators, own power, drops under 6 m
- Pilot needs
- Heading (its own), wind, GPS position, speed, rudder angle
- Mixed-brand autopilot data and control compatibility
- Data flows; screen control usually needs a brand match
- Legacy
- NMEA 0183 and SeaTalk via converters
NMEA 2000 backbone power and termination
is a powered bus: a backbone cable with a terminator at each end, a power tee fed from its own breaker, and drop cables to each device. Raymarine's and Navico's SimNet use different connectors but the same protocol; adaptor cables join them. The usual faults are a missing terminator, two power feeds, a drop cable that is too long, or a backbone that has grown by adding tees until the total length is out of spec.
The pilot's course computer is a device on this bus like any other. Its drive power comes from a separate heavy cable; only data goes over the network.
- One terminator at each end of the backbone
- One power tee, fused, from its own breaker
- Drop cables under 6 m; backbone within the spec length
- Network voltage checked at the far end
- Every device shows in the device list
Autopilot input and output data on NMEA 2000
The pilot produces heading from its sensor and consumes wind angle for Wind mode, position and speed for Track and , and route data from the plotter. It also reads rudder angle if a reference is fitted. Everything else on the network, from AIS to depth, is useful for alarms but not for steering. A pilot that suddenly loses Wind mode is usually missing wind data on the bus, not broken.
Mixed-brand autopilot data and control compatibility
Over a B&G pilot will read wind from a Garmin sensor and position from a Raymarine plotter. What usually fails across brands is control: engaging, adjusting and steering the pilot from the plotter screen, and one-touch route hand-off. Keep the pilot's own head as primary control on a mixed boat, and accept that the plotter may only display the pilot's status. A matched pilot and plotter is the easiest life.
AIS, radar and alarms
AIS on the network feeds CPA alarms on the plotter and, on some systems, on the pilot head. Radar overlay needs an accurate heading, which is one reason a good heading sensor or a improves more than the pilot. Set the alarms where the watchkeeper will hear them and confirm the pilot's off-course and XTE alarms also repeat on the plotter.
Older boats: NMEA 0183 and SeaTalk
Many Australian yachts still run NMEA 0183 instruments or original SeaTalk. Converters bridge them to , and a tiller pilot with an 0183 input can read wind and cross-track directly. Expect to lose some features and to spend an hour or two on sentence configuration. If the instruments are elderly, replacing them at the same time as the pilot is often the cleaner answer.
Give the network its own breaker
Questions
Frequently asked
Can I run a Raymarine pilot with a Garmin plotter?
Data, yes, over NMEA 2000 with an adaptor cable. Engaging and steering from the Garmin screen, generally no. Use the p70s as the control.
Why does my pilot show no wind?
Wind data is not reaching the bus: sensor unplugged, a failed drop cable, a converter not configured, or the instrument display that was bridging the data is off.
How many devices can I add?
Dozens, within the backbone length and power limits. Most cruising yachts have ten to twenty. Check network voltage at the far end after each addition.
Practise autopilot operation with an instructor
Habits are learned at the helm with someone watching. The training section explains what a good instructor covers and where to find one in your state.