Networking & Connectivity NMEA 0183

NMEA 0183 is the older marine electronics communication protocol, introduced in 1983, that allows devices to send and receive navigational data using serial RS-422 connections. While largely superseded by NMEA 2000 for new installations, NMEA 0183 remains relevant because many legacy devices, simple installations, and budget electronics still use it.

The protocol operates as a single-talker, multi-listener system running at either 4,800 baud (standard) or 38,400 baud (high speed). One device transmits data sentences while one or more other devices receive. This one-directional architecture limits the complexity of data sharing — to get two-way communication between devices, you need separate talker and listener wiring connections for each direction.

NMEA 0183 data is transmitted as ASCII text sentences with standardized prefixes that identify the data type. A GPS position sentence starts with $GPGGA, a depth reading starts with $SDDBT, and so on. This human-readable format makes troubleshooting relatively simple — you can actually read the raw data with a terminal program and verify what the device is sending.

Many modern fish finders include both NMEA 0183 and NMEA 2000 connections, providing backward compatibility with older equipment. Gateway devices are available that bridge NMEA 0183 and NMEA 2000 networks, allowing legacy devices to participate in a modern backbone network. If you have a mix of old and new equipment, a gateway device is often the most practical solution for integrating everything.