Understanding Marine Networking
Understanding Marine Networking Protocols
Different electronics use different network standards. Here's what you need to know before you buy.
NMEA 2000: The Universal Standard
NMEA 2000 (also called N2K) is the industry-standard marine data network used by almost every modern chartplotter, fishfinder, instrument, engine interface, and sensor. It uses a backbone-and-drop cable architecture, where a main backbone cable runs the length of the boat and shorter drop cables branch off to connect individual devices. If your electronics are from different brands; a Garmin chartplotter, a Lowrance fishfinder, and a Simrad autopilot, for example; NMEA 2000 is what makes them share data.
Ethernet (High-Speed Data)
Standard marine Ethernet cables carry high-bandwidth data between compatible devices; radar, MFDs, sonar modules, and cameras that need more throughput than NMEA 2000 can provide. Lowrance uses their own ETHEXT Ethernet cables; Raymarine uses RayNet. These are not interchangeable with each other or with standard IT Ethernet cables, as the connectors and weatherproofing are marine-specific.
Brand-Specific Protocols
Some manufacturers run their own proprietary networks alongside NMEA 2000. Raymarine's SeaTalk NG is electrically compatible with NMEA 2000 but uses Raymarine-branded connectors. Garmin's network uses standard NMEA 2000 connectors. Lowrance and Simrad (both Navico brands) share network compatibility. Knowing which protocol your devices use before you buy cables saves a frustrating trip back to the chandlery.
NMEA 2000 Cable Types Explained
The backbone-and-drop architecture means different cables do different jobs.
Backbone Cables
The main trunk of your NMEA 2000 network. Backbone cables carry the network signal and power down the length of the vessel. They are heavier gauge than drop cables and typically run hidden behind panels and through cable runs. Common backbone lengths are 1m, 2m, and 6m; plan your network layout before ordering to avoid having excess cable bunched inside a panel.
Drop Cables
Short cables that branch off the backbone to connect individual devices. Drop cables should be kept as short as practical; the NMEA 2000 specification recommends individual drop lengths no longer than 6m. Most devices come with a drop cable included, but extensions and replacements are often needed when mounting locations change.
T-Connectors
Not cables, but worth understanding in context. T-connectors are where drop cables branch off the backbone. Every device on your network needs a T-connector. These are found in the Connectors and Kits sections; if you're building a network from scratch, a starter kit that includes backbone cable, T-connectors, terminators, and a power cable is usually the most efficient starting point.
Matching Cables to Your Electronics Brand
Compatibility matters. Here's how the major brands connect.
Garmin
Garmin chartplotters and instruments use standard NMEA 2000 connectors for their network connections. Garmin's backbone and drop cables use the industry-standard 5-pin NMEA 2000 connector, making them broadly compatible across brands. The Garmin 0.3m drop cable suits tight installations; the 6m cable suits longer runs to helm-mounted displays.
Raymarine
Raymarine runs two parallel systems. Their SeaTalk NG network uses NMEA 2000-compatible connectors for the main instrument network. For high-speed data between MFDs, radars, and sonar; they use RayNet Ethernet, which is proprietary. Raymarine Alpha instrument displays use their own daisy-chain cabling system. Check your specific Raymarine product's manual for which connection type it uses before ordering.
Lowrance, Simrad, B&G
Lowrance, Simrad, and B&G all share network compatibility. A Simrad autopilot, a Lowrance chartplotter, and a B&G wind instrument can all communicate on the same NMEA 2000 backbone without adapters or protocol converters. All three brands use standard NMEA 2000 connectors for their instrument networks. For high-speed data connections between compatible MFDs, Lowrance uses their ETHEXT Ethernet cable format; Simrad and B&G use the same Simrad-branded Ethernet cables. If you're building a mixed Lowrance, Simrad and B&G network, the shared backbone compatibility is one of the advantages.
Actisense
Actisense is a specialist in NMEA networking products. Their backbone cables are brand-neutral and work across any NMEA 2000-compliant system, making them a reliable choice when you're mixing electronics from different manufacturers.
Planning Your NMEA 2000 Network
A few minutes of planning before you buy saves hours of frustration on the water.
Map Your Devices First
List every device that will connect to the network: chartplotter, fishfinder, instruments, autopilot, AIS, engine interface, and radar. Each one needs a T-connector and a drop cable. Count them up before you order.
Measure Your Cable Runs
Walk your backbone run and measure the distance from the network power point (usually near the battery or main panel) to the furthest device. Add 20% for routing around obstacles. This is your minimum backbone cable length.
Don't Forget the Terminators
Every NMEA 2000 network needs a terminator at each end of the backbone. Without them, the network will be unreliable or fail entirely. Terminators are found in our Connectors section; if you're buying backbone cable, add terminators to your order at the same time.
Starting From Scratch?
Browse our NMEA 2000 Starter Kits; these include backbone cable, T-connectors, terminators, and a power cable in a single package, removing the guesswork from a first-time network build.
Shop Marine Networking at Whitworths
Whitworths stocks marine networking cables, connectors, kits, and devices from Garmin, Raymarine, Lowrance, Simrad, B&G and Actisense; the brands Australian boaters actually fit. Whether you're replacing a single drop cable or building a full NMEA 2000 network from scratch, our team know these systems and can help you get it right. Browse the full range online or call into one of our stores for hands-on advice.