Know how: Replacing Outdated Electronics

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The author re-used the pod for the autopilot display and added a NavPod to house the MFD; the new wind/speed/depth displays are on the bulkhead

The author re-used the pod for the autopilot display and added a NavPod to house the MFD; the new wind/speed/depth displays are on the bulkhead

When we acquired our new project boat, a 1987 Pearson 39-2, it was evident that she was in need of much TLC. Not only had she been sitting forlorn and unloved in a boatyard for a couple of years, but those of her systems that were not original were a couple of decades old. Virtually everything was in need of overhaul or replacement, including her elderly suite of Autohelm sailing instruments dating back to the early 1990s, connected by the original Seatalk network. The speed and depth seemed to work fine, as did the autopilot—as far as I could tell—but the wind transducer at the masthead was frozen and the C80 chartplotter at the nav station was not only in the wrong place but a good 10 years old—a museum piece by modern standards. Oddly, there was one piece of modern tech in place—a Seatalk 1 to Seatalk NG converter—which surprised me, as there was no equipment on board that warranted it. When you’re upgrading, the first decision you have to make is whether to try to keep any of the existing instruments, some of which may be functioning perfectly well. Raymarine and a couple of third-party companies sell adaptors that would have let me do that. I could have just left the essentials—depth and speed—in place and tried to have the wind instrument repaired, but to be honest, I am done with trying to keep old equipment and outdated technology limping along. I wanted a plotter at the helm and the ability to interface with other electronics via Wi-Fi or the NMEA2000 protocol (see "Networking" sidebar below).

Removing the existing pilot display from its pod (left); The old (middle) and the new (right); the Seatalk NG cabling is much neater and the connections are foolproof

Removing the existing pilot display from its pod (left); The old (middle) and the new (right); the Seatalk NG cabling is much neater and the connections are foolproof

On the previous project boat, I had managed to get instruments from several different manufacturers “talking” to each other via the now outdated NMEA 0183, even though I am about as far as you can get from an electronics whizz. It was fun but took considerable trial and error, which I was in no hurry to repeat, so the decision to replace like with like was an easy one. I also had, sitting under my desk, a Raymarine es7 MFD, which, fortuitously, I had never gotten around to installing on the previous boat. Since the Autohelm days, Raymarine has developed its own NMEA2000 network, called Seatalk NG, and the new instruments would be connected to the plotter via this system.

My first project was to place the chartplotter at the helm, which involved first installing a Nav-Pod housing on the Edson pedestal guard, then running the plotter’s Seatalk NG and negative drain cables down through the guard leg and hooking them up to the battery and Seatalk connector. An NMEA2000 network cable incorporates a power supply, but important devices like MFDs and autopilots should have independent supplies. That took up an entire day by the time I’d been to West Marine and back a few times, and to celebrate I sailed for the next few weeks without doing anything else, as the old depth instrument still worked.

Soon enough, though, a box containing i50 speed and depth and an i60 wind instrument arrived, and I was ready for what I expected to be an easy weekend project. I was wrong.

One reason for replacing your instruments with those of the same make is that you may be able to re-use some of the old components. In the case of my old Pearson, the anemometer cable running from the mast partners to the instrument panel above the nav station was run through a conduit so tortuous and so packed with other wires that there was no earthly way of passing a new one through. Fortunately, the new cable was identical to the existing one, so I just cut it short and connected the two together on the existing terminal strip.

The transducer cables were another matter. I did not want to cut and splice these, and in any case the old in-hull depth transducer had to be replaced, which meant drilling a new hole in the hull. This done, a long conduit running from the bow to the nav station allowed me to cut the old cables, tape the new ones to the ends and pull/push them through using a couple of wire coathangers.

That spot of boat proctology was the easy part. The process of running the cables up the hull sides into the instrument panel, where the originals terminated in a rat’s nest of connectors, unlabeled wires from the preceding Datamarine system and scads of electrical tape, was a lengthy one, working blind and one-handed for the most part. Then I had to feed them through an extremely tight gallery up the coachroof side to the actual displays. How the previous installer got the old Seatalk cables with their big end fittings through there, I have no idea. I had to cut off the crimp connectors in order to get the new ones through, and the process took the best part of an afternoon.

The original instruments (left) and the new

The original instruments (left) and the new

And then—because no good deed goes unpunished—I had to run a Seatalk NG spur cable from behind the instrument panel, the “hub” of the new Seatalk system, to each side of the companionway where the displays were mounted. Suffice to say this was far from easy, what with the size of the end fittings, involving much cursing, the removal and replacement of sundry panels, drawers, locker bottoms and headliners, and some extreme boat yoga, again working blind much of the time. More than once I wished I had opted for wireless instruments.

In comparison to running cables, enlarging the existing holes for the displays—because of course the new instruments wouldn’t fit in the old holes—was a breeze. I screwed a piece of plywood to the back of the holes to provide something for the hole saw bit to grab and zipped them out one by one. I had already acquired new connectors for the transducer wires, and it was but the work of a few minutes to crimp them on, press them onto the instruments and connect the Seatalk cables. Cue the inevitable sense of satisfaction when everything powered up as hoped. Beer o’clock!

My takeaways from this project are predictable enough. Whether you replace like with like or choose a different brand from the old stuff, you are in for a fair bit of work that will make you understand just why it costs so much to have professionals install electronics. The “magic” of modern cabling systems is that they are in many ways idiotproof—the Seatalk NG cables just plug together so your instruments are daisy-chained or at the end of spurs, and those from other makers work on the same principles. If you can follow a simple diagram you’ll have no issues, and you’ll wind up astonished at how you suddenly turned into an expert electronics installer, perhaps fantasizing about billing yourself out at three figures an hour just like a real one.

But that’s the easy part. The physical process of removing the old gear and its cabling, and then running new cables and wires, can be much harder than you think, especially on older boats. And if you have to actually cut any of those N2K cables and then try to splice them together again, you had better know what you’re doing. Take it from me, read the manuals. Carefully.

You should be careful about measuring up, too. Those Seatalk cables and connectors are expensive, and in a pathetic attempt to save a few bucks I ordered a couple of cables that were too short (by a few infuriating inches), and then had to remove and replace them, in effect doubling the work time of installing them. Not only that, but each time that happened I had to wait days for the new bits to arrive, which is one reason this project dragged on over a month. Also, when frustration boiled over I would go and work at something else until I cooled off.

Left: the new instruments are daisychained; much boat yoga was involved

Left: the new instruments are daisychained; much boat yoga was involved

Speaking of saving a few bucks, I had not expected to have to replace the venerable ST6000 autopilot, which I managed to connect to the MFD through the adapter a previous owner had installed. And function it did until it threw an electronic hissy-fit on the way back from Maine, taking off in odd directions and making beelines for navigation marks. I suppose I could have traced the fault and repaired it, but I would not have trusted this mix of old and new tech again. Its replacement, an EV-200 unit, showed me just how easy it is to add something to an existing NMEA2000 network. It only took me a relaxed day to remove the old display, compass and brain and install the new unit, including running the Seatalk NG cable down the pedestal leg to the new actuator box, connecting the wires from the existing Type 1 linear drive, installing the compass and the display, and plugging everything together. I did make one mistake, soon resolved after a chat with Raymarine techs.

It was an expensive but fortuitous failure, as the EV-200 is a superior unit that has so far steered the boat some 1,200 miles over two months, through some pretty wild conditions.

I obviously did not do any damage to anything in this often awkward and painful installation, as the instruments, MFD and autopilot have worked flawlessly. If I can do it, you can too. 

The original crimps on the transducer cables had to be cut off as they would not fit through narrow gaps

The original crimps on the transducer cables had to be cut off as they would not fit through narrow gaps

Networking

The National Marine Electronics Association (NMEA) sets the standards for marine electronics networks. The best known is NMEA0183, which has been in existence for more than 20 years. Under this protocol, devices communicate with each other by sending and receiving data “sentences.” Some devices are “talkers” and send data (for instance a GPS antenna), others are “listeners,” and still others can both talk and listen. When there are too many interconnected devices, the signals can become diluted and the network can become overwhelmed. It also relies heavily on crimp and other connectors, which are prime sources of trouble.

NMEA0183 has been phased out by most instrument makers, who have adopted the NMEA2000 (N2K) protocol. This not only sends and receives data 50 times faster but allows many more devices—including those from different manufacturers—to be interconnected. An N2K network consists of a backbone cable into which you plug each device. The connectors are molded, eliminating the poor-connection scenario, and installation is much less complicated.

Some makers have come up with proprietary networking systems—Raymarine has Seatalk NG and B&G/ Simrad/Lowrance use SimNet—which are compatible with others via adaptors, while others use standard N2Kcabling and connectors.

Raymarine’s cables are color coded—blue and white for backbone, black and white for the spur cables—and are available in various lengths up to 30ft. The latter can be daisy-chained; the instruments I installed came with short lengths of spur cable. It is important to measure well because the cables and connectors are pricey and the cost soon adds up.

I used one five-way connector, to which I ran the power supply. With some trial and error, I was able to integrate the various spur cables running to various parts of the boat into the backbone cable.

February 2019

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