Similarly, I am thinking about switching to a Garmin chart plotter but would like to keep Raymarine radar RD418HD and Raymarine autopilot ST70- X10.  I have a Raymarine C120W chart plotter that  I can't get to interface with a Vesper AIS.

Can  I keep the RM radar and autopilot and switch to a Garmin chart plotter?

Posted by: @seadog47

I just upgraded to a Garmin 942xs with Fantom radar. I have AIS250  and a ST1000 autopilot I would interface. I think the problem isI can't do both because there is one NEMA 0183 in and out but the two devices are different baud rates. Can either be put onto the Seatalk to Seatalkng network I have a Raymarine adaptor cable that goes Seatalkng to N2K.as a spur that I will connect to the 942xs unit Is there a solution to my dilemma?

There are things that can combine/share 0183 data.  Yacht Devices makes a router that'll handle NMEA 0183 in-out and N2K.

But understand that most radar systems are designed to work on the same brand display ONLY.  Garmin radar on a Garmin display, Raymarine on a Raymarine chart plotter, etc.  

It turns out that the Raymarine AIS has a multiplexer built in. AIS is working via 0183 but the autopilot can be seen but I haven't figured out how to interface it. I think in the end I'll use the autopilot independent of the chart plotter using it mainly on long runs as, the more I read it looks like it can't be interfaced.

You will have three types of network when you're done.

The radar connects directly to the plotter with the Garmin Network cable (Ethernet  connector).

On the Garmin you have two NMEA0183 ports that can be individually configured. They are accessed via the power cable,

• Red +12V, black negative,
• NMEA0183 channel one: blue T1 (transmit), brown R1 (receive),
• NMEA0183 channel two: grey T2, purple R2.

From the AIS you have NMEA High speed signal which you connect the AIS NMEA T (transmit) to Garmin R1 and configure this in the Garmin plotter to High speed.

Then you connect Garmin T2 to the ST1000 connector. I don't have the numbers on the pins, but if you look at the soldering side you have counter clockwise negative 12V, +12V, NMEA+ NMEA- (which is ground) and Seatalk (will be used later). One pin is unused. The speed in Garmin for NMEA1083 #2 shall be NMEA Std.

To connect any remote control Raymarine S100 you do that on the connector pin for SeaTalk. It's only one wire, negative for SeaTalk is the same as negative for power.

The multiplexer in the AIS is not for NMEA communication but for antenna connection, so you can use the same VHF antenna for your AIS and VHF. The VHF antenna cable goes into the AIS and the AIS goes to the antenna. Since AIS250 is a receiver only, it has no GPS antenna. You could also connect the FM radio antenna to the AIS, if you happens to have a FM radio onboard.

I have had this configuration onboard my boat until I rebuilt my electronics and network (which I tend to to every year...). The ST1000 Autopilot is a fairly old design dating back about 40 years and hasn't gone through any major upgrades since it was design. That's why it has no communication newer than SeaTalk and NMEA0183 Std. I never had any success with the communication between my Garmin plotter and the ST1000 (ST2000), technically it worked but when I set the course on the plotter and routed this out to the ST1000, the course could deviate 30 degrees, and I never understood why.

Now I have switched to Raymarine EV100 which uses SeaTalkNG, which is about the same as NMEA2000, only the connectors differs. The remote control S100 signal is converted from SeaTalk to SeaTalkNG and it works fine, although a little bit slow.