Adding a NMEA-2000 Network

Project date: 2008

We will be adding a NMEA-2000 network to facilitate the addition of network enabled probes, such as a Bennett Trim Tab sensor, Fuel Tank Level sensors, and a display unit. In the future, we will be adding additional components to the network.

The first order of business is to sketch out the desired network. Mark each component with the connector's gender (M = Male, F = Female) to ensure you purchase the correct connectors. Since Maretron offers the most NMEA-2000 standardized components, I chose that brand to construct the network backbone.

The Multiport box design has been changed by Maretron since the one shown in the drawing, therefore the equivalent part numbers are the items required to match the box shown.



To save time, I am not going to show how to lay in the network backbone, but use standard good wiring practices, such as securing the cable with cable ties and so on. As well, I am not going to show the power wiring, as it is straightforward as well.

Note that I could have replaced the three Tees on the right side segment with a Multiport box, however, this scheme shows that either method may be used.

If you need more familarization with NMEA-2000 networks, please consult my concept page: NMEA-2000 Primer

You may also want to refer to power options for a NMEA-2000 network by reviewing my project: Remote Switching a NMEA-2000 Network.

Since the RayMarine C-80 MultiFunction Display (MFD) will be connected to the NMEA-2000 network, an adapter cable is required. When I did the project, RayMarine did not offer a pre-made cable, so I had to make one. RayMarine's SeaTalk 2 network is essentially a NMEA-2000 network, with of course, proprietory connectors.

RayMarine's E25041 cable has a SeaTalk 2 connector on one end, and a pigtail on the other. Fortunately, the color code of the cable matches NMEA-2000's standard color configuration. If you buy a Maretron field-installable connector, it will have the same color code, so its simply a matter of matching the cable color to the connector color. The Maretron connector is a FA-CM-ST which is a Male connector. If you need a Female connector, you would want a FA-CF-ST.

Here is the Bennett Trim Tab probe as it comes out of the box. Note that it has the older style Lowrance Blue connector, and is not compatible with NMEA-2000 standard connectors.

One thing I like to do when I construct projects is to go the extra step. In this regard, I am mounting the probe into an aluminum box. The Red and Green wires on the probe connect to the Trim Tab sending units, and I will splice the wires inside of the box. Cable feed throughs are used to facilitate the wiring exit/entry into the box.

As shown here, I have already replaced the non-standard Blue connector with a Maretron field installable Male connector.

In a similar manner, connect the two Lowrance Tank Level probes to the fuel tanks. Again, Lowrance Blue connectors need to be replaced, while Lowrance Red connectors do not.

The Bennett Trim Tabs sending units are located in the top of the hydraulic cylinders. The Bennett NMEA-2000 retrofit kit comes with new cylinder components to adapt existing cylinders. Since there is a new wire (red wire in the photo), you must drill a hole in the transom to feed the wire. Obvously, this hole needs to be properly sealed.

If you are not familiar with sealing holes, read my project in this link:

Proper method of drilling holes in fiberglass

Both LMF-200 and LMF-400 are flush mount instruments, and mount into standard 2"Dia and 3.5"Dia instrument cutouts. Why both instruments? OK - you got me. I happened to have a 3.5" dia hole in the dash left over from the removal of the old stereo wired remote. The logical choice to "cover up" that hole was the LMF-400. Turns out it is positioned in such a way that I can see the instrument when I am filling the gas tanks at the stern of the boat, so I typically put the display into "gas gauge" mode so I can see how full they are.

The LMF-200 mounted higher up on the gauge cluster is easier to see. And since both instruments can display a wide range of NMEA-2000 data, I can tailor each instrument to what is displayed.

The connection of both instruments are the same; the NMEA-2000 network (which also supplies power to the instruments), along with an optional dash backlight and warning buzzer. The buzzer comes with the kit, so you might as well find a location for it. As with the sensors, I had to modify the "blue" network cable for the LMF-200. But since I purchased the LMF-400 at a later date, it already had the newer "red" connector, which didn't require modification.

At this point, you should have the network backbone installed, along with the trim tab and fuel tank sensors. The Lowrance LMF display should also be connected at this point.

Apply power to the network. Then following the LMF display manual, calibrate the trim tabs. Next, program the fuel tank sensors. Note that as shipped, the fuel tank sensors do not have any tank information. When programming the sensors, you need to set the "instance", tank function (i.e. water, holding, fuel, etc), tank shape, and tank capacity.

What is an "instance"?

In NMEA-2000 lingo, an instance is a number that uniquely identifies the probe. There are two tank sensors, so one of them would be instance 1, and the second would be instance 2. By convention, Instance 1 would be the Starboard tank, instance 2 would be the Port side, an if a thrid sensor existed, instance 3 would be a center tank. This is not absolute, so consult the sensor's manual for each probe you own. When you program the probes, you write the data into the probe's non-viotale memory.

To elaborate further, the sensors typically come from the factory programmed with an instance of 0. Here is where NMEA-2000 manufacturer incompatibilities come in to play. The RayMarine C-80 display will recognize the Lowrance tank sensors, but only if they are programmed with instance 1 or 2. The C-80 will not recognize a sensor out of the box with an instance of 0, as 0 has no location (indicates unprogrammed). Only a LMF display unit will recognize an unprogrammed Lowrance sensor, and it is the only instrument that can program the sensor.

This is not untypical, as even Maretron probes will not be recognized by other instruments until a Maretron display unit programs them. However, if you ask Maretron, they will program a sensor for you at the time of purchase.

After connecting the RayMarine C-80 display (power off the NMEA-200 network when making the connection), you can see here that it not only recognizes the trim tab positions, but it also recognizes the Starboard and Port fuel tank sensors.

At this point, there is a basic working NMEA-2000 nework on the boat.

(Click on the drawing for a full sized version)




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