John Buoy Marine Communications (Part 1)


I haven’t written a lot about our boat, but this latest project needed a writeup.

I’m pretty big on knowing where I am as I plot the boat. We were lucky with John Buoy, as it has a pretty good control setup for a 1983 boat. (the electronics are much newer, and in mostly good shape.) The boat has both an upper and lower command station. From reading the documentation, I know that the upper station is the primary, and the lower was a factory option, and a secondary station.

On John Buoy, the upper station has

  • Full instrumentation for the engines and tanks,
  • The Sync gauge for the twin engines
  • A Lowrance LCX110c Chartplotter with Sonar
  • A Funuro 1623 Radar
  • A Standard Horizon VHF

The Lower Station has

  • A limited set of Engine gauges,
  • And a secondary Standard Horizon VHF.

That’s not bad. But I prefer having charts when I drive, so I setup a small Windows tablet with OpenCPN and a Bluetooth GPS at the lower station. That didn’t give me the current depth, but I could tack on the chart if I was getting into a shallow area and proceed with caution, or move up to the upper station and use the sonar for anchoring. ( I also have windlass controls at both stations)

That worked all summer. I also got an MMSI number for the boat, and added that to both Radios. they are pretty new, and support the one-touch mayday button. This is a great feature, partially for myself, but more for Yulia or Sasha to use if I get injured or knocked out. With one button they can get help. But for that to be really effective, it should be getting a signal from the GPS to transmit that data as well.

And this is where things got tricky.

There are a few communication standards to get marine Electronics to talk.

  • NMEA 0183 is a straight serial protocol (based on RS-422 apparently) This means linking actual wire-to-wire.
  • NMEA 2000 is a communications bus, similar to older Ethernet 10 Base2. It’s also really expensive for connectors.
  • Signal K. This is a new Open Source protocol, where you pull in several older devices into a computer or device and you can rebroadcast the signals to use. This can work several ways, but the handy one is straight over a local WiFi network.

Checking over the boat, I had nothing talking. The Chartplotter had wires for 0183, that appeared to be hooked up, but they didn’t work. The Radar wasn’t wired to anything. (The actual Comm wire was an option that wasn’t there) Starting out I wasn’t sure what to do with all this. So I started with getting the Radios wired up. To get hard wired communication working, you hook the “Talker” wires of a device up to the ‘Listener” wires of the next (according to spec, you can put three listeners on one talker) It took a lot of messing around, especially since the color coding in the documentation was wrong for the chartplotter, but I got the Lower VHF connected to GPS, and after finding and fixing a short in the Upper VHF, got that talking too.

So now my VHF radios have my coordinates in case of an emergency. That’s a good safety addition. But I still didn’t have any sonar at the lower con. This was going to be tricky. What I found for a solution ended up being much more generally useful.