The Offshore Voyaging Reference Site

Maretron—Better NMEA 2000 Cabling

A couple of years ago I installed a rudimentary NMEA backbone on Morgan’s Cloud to support the new B&G Zeus³ plotter we bought to replace our venerable, but sadly departed to the electronics graveyard, Northstar GPS, and to back up our primary navigation system.

This year I have added to that network to support a replacement autopilot brain.

When I’m doing this kind of thing, my scepticism about the quality of most marine electronics tends to kick in, and never more than when I looked at the chintzy NMEA 2000 cabling included with the plotter, autopilot and related gear.

And I was particularly concerned given the potential for NMEA 2000 networks to completely shut down and take every piece of connected electronics with them. This is the great weakness of daisy-chain networks of any type, and doubly scary on a boat where one drop of water in the wrong place, a chafed cable, or a corroded contact can bring the whole thing down. See Further Reading for more on this.

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Marc Dacey

Thanks, John. I’ve just purchased a 9 inch B&G Vulcan for my pilothouse, “liberating” the previous 7 inch Vulcan for use at the outside helm, and I was looking for a more robust way to connect it all together. This is helpful and, I agree, well worth the fairly trivial extra cost.

Marc Dacey

I like the use of that multiport box, too. I’m already in the market for one of those Actisense 0183-2000 converter gadgets, so I can feed compass, GPS and AIS data to my Furuno radar display in a more “tidy” fashion. More jobs over the winter!

Matt Marsh

Lest anyone be tempted to buy shielded cable by the 100m spool and terminate it themselves with field-assembled connectors…. I assure you, no matter how good you think you are at cabling, you will NOT match the reliability of the Maretron factory-made cable assemblies for anywhere near as cheap as the Maretron price.

Philip Wilkie

Totally agree. Like John I started life as an electronics techie, so I used to be very familiar with soldering, and to be blunt most people who aren’t doing it all the time are pretty bad at it.

Chuck Batson

Agreed, although pre-assembled isn’t always an option if the cable needs to run through a tight space the connector won’t fit through.

Alastair Currie

I just upgraded my Autopilot to a new Raymarine Unit and was at my wits end trying to connect their Seatalk NG backbone connectors together. It was straight forward enough, align the two arrows, push together and twist the collar, but could I get the collar to engage with the pin by twisting! I actually split one of the plastic collars thinking it must be a tight O ring by firmly pushing the parts together and twisting the collar. I will be expanding the network when I replace the plotter, so a timely article, again! And the price of extension kits ….

Dick Stevenson

Hi John and all,
Yes, I agree. Maretron is a quality outfit.
When I re-instrumented back in 2012 I ripped out all the old data wiring and started anew with Maretron and I do not believe I have had a hiccup since. I found their N2K designer really helpful but posed (for me) a steep learning curve (it is likely more user friendly now). I also shied away from the more complicated, but very tempting, Maretron offerings (such as a weather station at the top of the mast), but friends have given good reports of this piece of kit. Mine was a Furuno-based instrument display/brains system, which, in hindsight, used some of the same senders/sensors that Maretron uses.
And, what Matt says is entirely accurate: buy the pre-made cables. That said, I used a handful of the field-use terminals (when cables had to be snaked through small passages) and they have stood the test of time. Having a couple of right angle terminals really helped a couple of times.
Oh, and as I remember, I ordered straight from Maretron. And agree: they were very helpful.
My best, Dick Stevenson, s/v Alchemy

Philip Wilkie

Just for the sake of curiosity, the Maretron N2K media looks very much the marine equivalent of the the original industrial DeviceNet media specification.

Maretron look like they’re sourcing a very similar product, just with different colours. Maybe even from the same factory I’d hazard a guess.

DeviceNet is an open protocol network stack, targeted at industrial applications, that originally came from within Rockwell Automation in the early 90’s. The physical layer, like N2K, is based on the original Bosch CAN chip now used in tens of millions of vehicles worldwide. The underlying tech is actually exceedingly reliable; the problems arise when in industrial or marine settings the end user puts together networks without reading the manual thoroughly.

In my experience 99% or more of problems that customers encountered were due to cable problems, or failing to observe to design rules on terminators, dropline lengths and power supplies voltage drops.

Matt Marsh

That wouldn’t surprise me. NMEA 2000 is essentially just some marine-specific messages added on to the widespread automotive CAN standard SAE J1939. Its cabling and connector standard *is* the DeviceNet spec, copied word for word.

Also, I still have not forgiven Raymarine & Simrad for their utterly moronic, brain-dead marketing decisions to slap their own proprietary connectors on what is still supposed to be NMEA2000 with a DeviceNet physical layer underneath.

Steve D

In short, I agree. I’ve used and been a fan of Maretron almost since inception, I specify it on virtually every new build and refit project. It is relatively easy to design and install, and program and its ability to accept generic non-Maretron devices is also very attractive (I can select my own networked smoke/CO detectors, for instance, one that includes the features I wanted). I’ve used it on vessels from 26 to 100 feet. Yes, it really is that good.

Maretron is owned by Airpax (they were a 50% owner for years and last year completed the merger), manufacturer of circuit breakers and other electrical equipment. When this merger occurred many expressed concern; While I am often concerned about such acquisitions in the marine industry, as they frequently spell lower quality and poorer service, in this case I wasn’t worried as I’ve known Airpax to be a great product and believed this would only enhance the Maretron brand.

Steve D

And I can give you half a dozen other examples of marine industry acquisitions that resulted in lower quality products and support, it’s usually bad news, this one seems to be an exception. I wrote an editorial about it a few years ago

Paul Rutherford

If you only have a few units to link this is an equally good quality option – truly plug and play (for up to 8 connections) in my experience:
They also do a 4 connection unit.

Craig Harmon

John, you mention the unique tees at which supplemental power can be added. I have a NMEA 2000 system with a fair number (15+) of devices on it. Sometimes when I lean on a power-hogging piece of equipment like an electric winch or bowthruster, I get a momentary “low CAN BUS voltage” alarm, even though my battery bank SOC may be very high at the time. I wonder if adding in some power at a second location in the backbone might ameliorate this? (I note that, since putting into practice your excellent tips on backing boats that don’t steer in reverse, I’m leaning on the bowthruster less and less. Ha.)

Philip Wilkie

In addition to all of John’s suggestions above (which I’d try first as a matter of good practise), I would also run my N2K network power from an Isolated DC/DC converter supply.

Victron Orion-Tr 12/12-18 (220W) would be a good choice. This way it really doesn’t matter what happens on the battery side, the output side to the network power will be tightly regulated.

Craig Harmon

Thanks, John and Philip. I will check cable sizes and connections. The builder (Valiant) seems reputable and doesn’t appear to have skimped on too much, so with luck it is connections or total bank size. I have only 4 Lifeline batteries (brand new). That just might not be enough. (And I like the converter idea, though I do understand the risk of treating a symptom rather than The disease.).

Dick Stevenson

Hi Craig,
I have a Valiant (V-42-128) and I suspect the wire gauge sizes are more than adequate and I suspect your batteries are group 31s which, in new AGM Lifeline, should be way more than adequate to power a complex instrument package (~~~400 Ah), even when a powered winch demands current. I also have a fairly complex N2K Maretron based set-up and have for 12 years or more, but do not have the big load items you mention.
If I remember correctly, Maretron has a diagnostics capability that they sell which might determine any glitches in the N2K system that would contribute to the warning you receive.
Those big current items are an amp-sink, but the bow thruster, I would guess, is only used when the engine is on.
I would lean strongly against the DC to DC converter until you find the problem. There is something going on which can only cause problems in the future.
When trouble-shooting, I always ask myself: “What just happened?” In your case you got new batteries and I would start there and look at any connection that was touched. Was the N2K package working well before the new batteries?
It could be as simple as there being a stainless-steel washer used on one of the battery terminals that is strangling the current when big loads occur.
I would start at the batteries and take apart, inspect, clean, goop with copper-kote or the like and reassemble every connection from battery to where the N2K picks up its power. Don’t forget the negative side. Document every terminal wire as you go along. And, yes, the positive distribution posts are a pain to get to (at least on my boat) but need to be worked on also.
Let us know what you find.
My best, Dick Stevenson, s/v Alchemy

Craig Harmon

Thanks John, Philip and Dick. I will go into detective mode. One further interesting fact that occurs to me after thinking through the helpful advice: My bow thruster is not wired through the DC panel. It is 24v and its switch activates a solenoid that puts the two house banks in series. That circuit has its own 400a fuses and big Guest switches. if the low voltage is occurring with two machines (bow thruster and winch) that do not share any cabling on the positive side, must any high-resistance connection causing unacceptable voltage drop be on the negative side? Just a thought. I’ll investigate and report back. Thanks again.

Robert Hellier

Hi John,
Is there any reliable solution for NMEA2000 cabling when one has no choice but to cut a terminator? I had to do this for the cable from my wind instruments after spending 3 hours on a bosun’s chair trying unsuccessfully to pull the cable and its fat terminator through the mast. At the moment I’ve just connected the 5 wires of the wind instrument cable to the boat’s NMEA2000 network via an open bus bar. I intend to replace it ASAP – but with what? I see Matt’s post about unreliable on-site splicing so what else to do?

Timely article! Thanks.

Dick Stevenson

Hi Robert,
Maretron makes field-attachable connectors/ terminals for just that situation. They come male and female and in right angle which is very hand in some situations. I have used them in protected areas for 10+ years without a problem.
You might ask Maretron about a top of the mast connector and how to weather proof it. Ham radio people put me on to coax seal a while back that is marvelous for this function.
My best, Dick Stevenson, s/v Alchemy

Robert Hellier

Thanks Dick. I’m looking at the Maretron field connectable connectors now :>)


Marc Dacey

Another vote for Coax-Seal, which has also been recommeded to me by amateur radio pros for our upcoming SSB installation. (

James Sarrett

I second everything that’s been said here, but I want to emphasize 2 points most people miss. Buss bar/barrier strips (and ring terminals) outside in the salt and spray are notoriously unreliable. Pretty much any watertight connector is a vast improvement. If you’re in a tight spot (e.g. the masthead) I actually like heat-shrink crimp-on butt splices filled with dielectric grease. Just be sure you get the right size so the heat-shrink will seal on the cable. leave plenty of service loop and if you have to replace something, just cut it off.

The second and more insidious problem is that N2000 is a CAN-bus and as such is not designed for a star topology. In general that means that without an active repeater you shouldn’t run a line off a backbone t-piece for much distance at all, let alone up a mast. In general you should keep T-offs less than 1m from the backbone, though in the real world you’ll get away with longer. The suggestion of adding a separate bus up the mast (and the associated terminators on each end) does solve that problem. Otherwise, you really should be running the backbone up and then back down, to not have a very long spur off it.

CAN busses with lots of t-offs that go long ways will work, but will also fail randomly and intermittently, as this effectively ruins the termination. Different silicon in different devices will all behave slightly differently and with so many things talkign on the bus normally it is very difficult problem to diagnose without an oscilloscope.

Petter Mather Simonsen

I also have the Maretron multiport boxes installed on the vessel and can attest that this is a really good piece of kit that works and that simplifies cabling. Prior to installing that, the original installer of the gear had just daisy chained some components. Apparently not good, nor recommendable practice.
It is possible to find these components at a favourable price on ebay.

Iris is in principle a 24v vessel. To feed the 12v electronics I have cabled in an isolated 24-12v DC/DC converter from Mastervolt. In principle is might also be an advantage to have a 24-24v DC converter to feed sensitive 24v. I nearly fried my 24v electronics on a longer passage when the regulator of the wind generator called it a day – and the generator started to produce voltages above 30V.


Ben Ellison

My boats have many high-quality Maretron (and Actisense) cables and connectors, as well as lots of industrial DeviceNet gear I’ve bought on EBay. But you have to be careful because the NMEA 2000 cable and connector standard is a subset of DeviceNet. I tried to explain here:

Ben Ellison

“A clever power T that can be connected to two power sources one primary and the other backup”

Not really. What the Maretron Micro/Mid PowerTap does is supply separate 12v feeds to each leg of the network, thus reducing possible voltage drops at the far ends. (And Maretron Mid size cables can also reduce voltage drops.)

It’s also female on both backbone sides so that exposed male pins are never hot even if you break into a network while it’s powered up.

Marc Dacey

Thanks, Ben. I’m about to order a whack of Maretron cabling and connectors and an Actisense device to allow my radar to display AIS and bearing data from the NMEA 2000 backbone. It’s the quality of the commenters as much as John and Phylis’s excellent writing that keeps me coming back. Oh, hey…I can do italics now! Nice.

Stein Varjord

I just read an article on Seabits about a new terminator from Actisense. Steve has mostly used Maretron the last 10 years, and still does, but this terminator seems like a smart piece. Firstly it’s universal, meaning it has a female plug in one end and a male connector at the other end. The unused one is covered by an included plug. The terminator also has an LED that lights up green when there is more than 9 Volts present and the network is terminated correctly. Pretty useful.
The article:

Marc Dacey

Stein and/or John, I hope this question isn’t off-topic, but I intend to order the Actisense smart terminator along with a range of these Maretron NMEA 2000 cables and T-fittings. I am slightly confused (and a call to the local chandlery didn’t clarify matters) with the best way to hook my Furuno 1815 standalone radar into my NMEA 2000 network with a NMEA 0183-NMEA 2000 “converter”, such as the Actisense NGW-1-ISO device (

My goal is to feed data from my heading sensor and AIS source already “seen” on my plotter to my radar to enhance its functions and, in essence, to use it as a second plotter, minus the chart overlay. I feel because I don’t need to take any 0183 data from the radar, but simply to feed existing NMEA 2000 strings to the radar, the “standard” NGW-1 is all I need, not the NGW-1-ISO-AIS device, which converts 0183 output to 2000 data. While I could use some sort of terminal block setup to transfer between my base VHF AIS target data fully in 0183, this solution seems tidier and more comprehensive. I realize I will have to fiddle with the baud rates on the radar, but that’s not an issue for me. Thank you. This is a very helpful thread about the pitfalls of too much ambition in the networking department.

Marc Dacey

Understood. Thank you, John.

George Gruebling

I agree regarding the Maretron quality and like using myself. However, I find the field connectors to be horribly tedious. Also, depending on where you are assembling them, (often in a tight dark space with is why your are using it in the first place) the connection with the 5mm lengths of wire and tiny screws can be suspect. They are better suited to assembly on a lab bench.

I have really like the Phoenix solution. Phoenix is an industry leader with quality stuff. Here is an example but there are other options depending on needs:

Illustrating the ease of assembly:

Dick Stevenson

Hi all,
I believe that all that has been said about the benefit of manufactured connectors and terminals is accurate, but I am also clear that there are many of us, when re-instrumenting their boat, who will be compelled to use a few field connectors where snaking the terminals/connectors through tight spaces proves unworkable.
And, yes, doing the terminals is fiddly work, but it is straightforward, basically un-skilled work, where going slowly and carefully and inspecting makes up for having no great skill and experience. At least, that was my experience, when I re-instrumented Alchemy 10+ years ago and none of the ½ dozen or so field installed terminals have given me any trouble.
A couple of suggestions:
Practice where comfortable and there is good light.
Leave a sizable service loop so you are not working right against the instrument you are connecting to: its length will allow much easier work and will allow for doing the work in a more comfortable position.
Ensure the wire is well secured near the connection so there is no chance of vibration.
Document/label every field connector on the schematic you are planning to make of the whole re-instrument array.
My best, Dick Stevenson, s/v Alchemy