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Marine Electronics Journal Blog

Displaying engine data on a NMEA 2000 network


One big advantage of NMEA 2000® is the ability to connect devices to the backbone by simply “teeing” in a drop cable—data is shared and displayed seamlessly. Unfortunately, sometimes it’s not quite that simple when it comes to integrating engine data.

The information below, excerpted from a longer article in Marine Electronics Journal, is not intended to turn you into an electronics tech. Rather, our aim is to help you understand a few of the issues involved in case you’re thinking about displaying engine speed, temperature or oil pressure on your chartplotter.

By Michael Crowley

The hardest part about integrating engine data on a NMEA 2000 network is getting the connection from the engine to the display or to the gateway—a device that in effect converts dissimilar data into a common language—according to Zack Floyd of Gemeco Marine Accessories in Lake City, SC. The first thing to do is find out if the engine supports J1939, which is the open “standard” for powertrain networking and communication that was developed by the auto industry. Essentially, J1939 defines how data is communicated between various control units on a network.

So far so good, but getting that information may not be so easy because there really isn’t a good resource to confirm whether or not the engine offers J1939 output, says Kip Wasilewski, who works for NMEA 2000 equipment maker Maretron in Phoenix, AR. In many cases, documentation manuals have been lost or misplaced.

Maretron offers a database on its website with engine manufacturers and model numbers that output J1939, but all engines aren’t on that list. And getting information from an engine manufacturer can be difficult. “Most engine manufacturers are large companies,” says Wasilewski, “so trying to reach an individual who has the ability or access to answer that question is very challenging.”

If there isn’t a built-in solution or a “turnkey gateway” to get engine data to the NMEA 2000, it often takes some discussion between the customer, the technician and the engine manufacturer to determine if a powerplant outputs J1939. Getting engine data on a NMEA 2000 network isn’t always that involved, but Floyd says that “almost every engine interface we deal with is at some level custom.”


Multiple engines

Things can also get a bit involved when trying to bring engine data from more than one engine onto the NMEA 2000 network. John Barry at Technical Marine Support in Pleasant Prairie, WI, knows this well, because most of the boats he works on have at least two engines. This requires “instancing,” which is a procedure to distinguish between identical devices.

A boat he recently worked on to bring engine data on to a NMEA 2000 network had two engines with J1939 translators. The NMEA protocol goes from port to starboard, so the port engine would be instance 0 and the starboard engine instance 1. The problem came in identifying those two engines on a chartplotter display. “The ability to do that instancing from the menu of the manufacturer is spotty at best,” says Barry.

He used a Maretron USD100 gateway to log in with his laptop to “instance those J1939 translators then put them on the network.” Until then there was no facility in the chartplotter’s menu that could set one engine as instance 0 and another as instance 1, or assign them as port and starboard. He said things can get really confused when you’re dealing with three or four motors or a generator and a motor.

Electronics manufacturers can add to the confusion, whether you are trying to display data from one or multiple engines. One example offered is a new chartplotter that sports a J1939 port. “The tech support was telling us weird stuff,” says Barry. One person told him that only one motor could be brought to that port. The other motor had to be put to a gateway, then into a NMEA 2000 port. Then he was told by a different person, “No, just backbone them together and put both into one port.”

Assuming the engine data does make it onto the NMEA backbone (like the drawing at left), then there’s the issue of the display. Is the device NMEA certified or is it described as a NMEA-compliant product?

The NMEA guidelines for a certified product say, among other things, it can’t be daisy chained and is supposed to use micro-C connectors,” says Kevin Boughton at Midcoast Marine Electronics in Rockland, ME. “It has to have specific language, protocol and certain sentences.”

A NMEA-compliant product will generally function as a certified product, “but there will be some issues, connectivity or sentence that’s not quite certified. That could cause a problem.” Boughton advises against putting a non-certified product on a boat.


Converting data

One gateway that converts the J1939 protocol to NMEA 2000, whether it’s an engine or a genset, is Maretron’s J2K100. “It is very flexible,” says Wasilewski. It can output to a Maretron display or to a display from another company, as long as that display accepts NMEA 2000 engine data.

The J2K100 is for digital engines. Operators of analog engines have at least two options: the Actisense EMU-1 engine monitoring unit and the RS11 from NoLand Engineering in Melbourne, FL. The EMU-1 has a PC-based configuration tool that allows settings to be changed to match up with a particular engine. It can monitor two engines.

NoLand Engineering’s RS11 can also be used with just about any analog engine and for either a single or dual-engine installation.

Essentially both the EMU-1 and the RS11 “do the same thing,” says Peter Braffitt of Gemeco Marine Accessories, the US distributor for UK-based Actisense. “They take analog data, whether it be voltage resistance or any analog signals and convert it over to NMEA 2000. They are programmable, so assign each channel and tell it what type of sender is on there, what the range is and then the output matches the gauges or the instrumentation.” It doesn’t matter if it’s a voltage based or resistance-based sender.

Both the EMU-1 and the RS11’s configuration tool allow you to program the system to tell it that one of the channels is oil pressure, its range and program in alarm levels.

All three gateways are “listeners” only. They only listen to data from the engine. They do not allow information to travel from NMEA 2000 back into the gateway and engine. Floyd says that feature in a interface is very important. “They can’t just spit information back out to the engine.” He figures that feature has helped engine manufacturers be more comfortable with NMEA 2000.


Engine maker cooperation

Are engine manufacturers buying into the need to make engine data accessible for NMEA 2000? Some have. For instance, some Volvo engines output NMEA 2000. “You don’t need a gateway,” says Wasilewski. All that’s required is the standard NMEA 2000 micro-C connection “on the engine that you could tie into as a drop on the NMEA network.”

Wasilewski thinks some engine manufacturers are seeing the benefits of NMEA 2000 in the marine market “by offering that or if nothing else by offering J1939 that can be converted relatively inexpensively.”

But the phone conversation can sometimes still be fairly short. A couple of times Boughton has called an engine manufacturer looking for information. “We don’t do N2K. End of story,” says Boughton. Other engine dealers are more cooperative.


Keep it simple

No matter how hard or easy it is to put engine data on a multifunction display, there are those that question the wisdom of putting it there in the first place. “Why do you need a tachometer on your Garmin chartplotter, when you have a tachometer next to the chartplotter?” says Barry, who admits to not being a believer in repeating data needlessly.

Boughton figures a lot of recreational boat owners see it as a neat gimmick. It’s the “I have the ability to do it, so I want to do it,” thinking. Even though, as Barry also notes, “most recreational boaters have their engine panel right in front of them.”

For a fly bridge that lacks that engine gauge, the instruments down below can be tapped into and the information sent up to the fly bridge.

Some recreation boat owners see it as a way to enhance what’s presently available, hoping they can get “fuel flow and things like that on the display that the engine data is not giving them,” says Boughton, but he feels that in most cases, it’s a “very large expense for very little return, but some insist on it.”

If a customer does elect to go with NMEA 2000 engine integration, it’s probable that all the engine data won’t be able to be displayed, which is why Boughton says to “just go for the basics: rpm, oil pressure, temperature.” Barry agrees. “Tach, temp and oil are the three main ones,” he says. “If you don’t over rev it, don’t over heat it and don’t run out of oil, you probably won’t hurt it.”


About the author

Mike Crowley was Boats & Gear Editor at National Fisherman and WorkBoat magazines for many years. He has written several articles for MEJ.

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Comments | Leave a Comment
Page 1 of 2 ( 9 comments)

Darryl:(3/27/2017 10:17:15 PM) "Putting the MSRP with each unit reviewed would have been helpful. If each unit was actually tested, the reports on each unit would have been helpful too.

Thanks Darryl---we generally don't mention prices due to confusion over so many variations---MSRP (mfg. suggested retail price), MAP (min. advertised price), MRP (min. resale price) and then there are internet prices on some websites that go their own way. But your point is well taken--buyers need to know if something is in their price range. We'll work on it.
There is independent testing of some of these products on sites like but the information we receive from manufacturers rarely cites the results of any shootouts they may conduct against the competition's products. "
Laurie Seibert:(2/16/2017 2:00:20 AM) "Thanks EV Collier for sharing this informative blog. It is important to know the causes of EMI filters. We use these parts in our daily life in the electronic products so we should know that what are the causes are cures of EMI Filters.

Great job and keep updating!

Laurie Seibert"
Yes:(2/10/2017 7:22:40 AM) "EMI/RFI filter causes and cure. There are very few people who share such information with everyone. I was looking to read such informative blog!

Great job!

Lisa Wilson
hugo:(1/30/2016 2:00:32 AM) "Why is no integrated ais transceiver available? Only recivers.


Each AIS system consists of one VHF transmitter, two VHF TDMA receivers, one VHF DSC receiver, and standard marine electronic communications links (IEC 61162/NMEA 0183) to shipboard display and sensor systems (AIS Schematic). Position and timing information is normally derived from an integral or external global navigation satellite system (e.g. GPS) receiver, including a medium frequency differential GNSS receiver for precise position in coastal and inland waters. Other information broadcast by the AIS, if available, is electronically obtained from shipboard equipment through standard marine data connections. Heading information and course and speed over ground would normally be provided by all AIS-equipped ships. Other information, such as rate of turn, angle of heel, pitch and roll, and destination and ETA could also be provided. Check out:"
Islander Sailboat Info:(12/4/2015 9:49:32 AM) "Great post!! This is the missing introduction I've been looking for. Thank you for taking a complicated subject and making it very easy to understand."
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