Combining old and new instruments
- upgrading from Sea Talk to Sea Talk NG and combining NMEA 0183 with NMEA 2000


There's always an unpleasant surprise involved

The following takes place in Mauritius in September 2012.

After our previous lay up in Phuket, two of our Raymarine ST60 instruments showed signs of dying. I suspect that the direct cause of this was the flooding of our storage locker at Boat Lagoon. A lot of other equipment went out of order as well, for instance a laptop containing our communication and navigation software. Before we reached the Maldives there was only ad hoc activity on the ST60 Multi display. The ST60 Speed instrument was working, but the display had a large dark spot in the centre making it difficult to read the digits.

Scorpio's sailing instruments are (or were): 4 ST60 in the cockpit (multi, depth, speed, wind) and 2 ST60's below deck at the nav-station (multi - wind). These were all linked to an autopilot 6000+ control head via Sea Talk wire. In addition we have a second autopilot with an ST6002 control head, but those are on an isolated circuit and outside the scope of this story. Navigation information was provided by an old Garmin 126 GPS feeding NMEA 0183 data into the Sea Talk system. Also the GPS started to grow a black area in the middle of the display and required retirement.

The easiest, and cheapest, way to fix the problem would have been to buy two new ST60 instruments, the ST60 Speed and ST60 Graphic (which has replaced the Multi in the ST60 line) and added a simple Garmin display to fit in the cut out hole of the old one. The dash board in the cockpit was built less than a year ago and I hated the idea of starting to cut new holes in it. Installing the new stuff would probably only have taken 10 minutes and no new wiring would have been required.

That's what I had in mind entering the marine store, but I ended up buying two Raymarine i70-displays and Raymarin's e7 multifunction display!

The old ST60 and the new i70 side by side, and finally working

The main problem in this case was that the new and the old instruments do not talk to each other and cannot share information. The old ones use the SeaTalk (Raymarine's old proprietary system) and the NMEA 0183 protocols, while the new instruments use the SeaTalk NG (for "next generation") and NMEA 2000 protocols. No problem, says Raymarine, just put a converter in between. It turned out, it wasn't exactly that easy. It never is, I should know that by now - all projects escalate, as I have noted before. The first surprise had to do with the autopilots. They cannot be connected to the instruments anymore! In the old SeaTalk system I had just connected the autopilots in series with the ST60 instruments, but this is not possible in a SeaTalk NG installation. The autopilots have to be directly connected to the course computers. This fact can be found in the (electronic) manual, but was never told to me by Raymarine. This finding was very unpleasant because it required pulling wires through difficult locations and required longer wires than I had prepared for. And you cannot get spares and parts in Mauritius.

The other surprise, which is not mentioned anywhere in the documentation (at least I haven't found any) was the fact that the old analog ST60's that I have (depth and wind, second from left and second from right in the photo above) do not understand any information if the transducers/sensors have been connected to the iTC5 converter. These sensors have to be connected directly to the old instruments! When I first connected the depth transducer wires to the iTC5 we got the correct reading on both i70's, but nothing on the ST60 Wind! Fortunately I didn't cut any cables before discovering this.

The iTC5 during installation The ST1 to STng converter kit. In addition you have to build a STng "backbone"

I knew I would have to cut new hole in the dash board, and I cannot blame anybody else for that. The size of the e7 is smaller than the combined size of the old Garmin and the old ST60 Multi, which it was going to replace. Therefore I had brought with me, on my recent trip to Finland, a sheet of polycarbonate, which I used to mask the hole. The sheet was transparent, so after cutting the hole I had to spray paint the mask.

The new e7 with a masking frame of polycarbonate The old setup (woodwork is less than a year old)

The third surprise was about getting a GPS signal into the e7. Remember it was supposed to replace the Garmin 126 in that respect (and of course it does a lot of other things too). Foolishly I hadn't given this much thought, just assumed that I could connect the existing Garmin antenna to the back of the e7. No, no, no.

Okay, the e7 does pack an internal GPS. But the installation location at the navstation below deck was not a place where you can be certain of a reliable GPS signal. Connecting an external GPS is done either via the SeaTalk NG system (already in place as described above) or via an NMEA 0183 connection. At this stage there was no place I could buy a GPS to connect to the SeaTalk NG "backbone", and therefore my only option was to take back the already retired Garmin 126 and temporarily re-install it, just to provide the e7 with an external GPS signal. Very clumsy, but it works. I have another identical Garmin 128 installed in the cockpit, but I couldn't get the NMEA signal down to the navstation for some reason (maybe the distance is too long).

Regarding the size and fastening of the i70's: Fortunately the cut out hole dimensions of the ST60 and the i70 are identical (and I had made sure of that). However, Raymarine has decided to design the fastening screw differently. The screws are in different places, necessitating drilling new holes (our panel in the cockpit is made from stainless steel) and the handy tool-less knobs are gone. On the other hand, this new design may be more water proof.

The fastening arrangement is different.
Red arrows indicate old holes, blue indicate old knobs
The e7 can be operated on the iPad wirelessly from the cockpit

And now, let's see how the iPad and the e7 work together. But thats another story.