All but a hardy bunch of self-confessed minimalist sailors would probably agree that they would like to modernise their boat by adding some extra electronics.

A shiny new multifunction display, perhaps, or an ultrasonic anemometer at the masthead; maybe a digital tank-level sensor or an engine monitor.

As data has expanded, so has its potential to keep you safer at sea.

Electronics are expensive, though, so there is real value in keeping old instruments alongside new additions when you modernise your boat.

The problem arises because they ‘speak’ different languages: modern equipment uses the newer NMEA 2000 (N2K) data standard, whereas older instruments tend to use the slower NMEA 0183 protocol, SeaTalk or even analogue.

Luckily it can be simple to convert between the two thanks to a range of networking add-ons.

‘Replacing legacy NMEA 0183 instruments with newer NMEA 2000 devices can be a very expensive process, so getting 0183 instruments communicating with N2K devices is a great way of completing your boat’s network,’ confirms Justin Cohen of industry-leading networker Actisense.

‘Many of our customers are end users and boat enthusiasts, with no formal certifications or installer training.’

What is NMEA?

National Marine Electronics Association, and it has long been the global standard for networking marine instruments.

It defines what data a ‘talker’ instrument generates and how it is transferred to other ‘listener’ instruments in electronic ‘sentences’.

Each sentence is designated by five letters — for example GPGLL means the following numbers refer to your latitude and longitude — followed by a string of numbers.

NMEA’s widely used 0183 protocol, launched in 1983, had a baud rate of 4,800 bits — that is, it could transmit 4,800 noughts and ones each second, equivalent to around 450 characters.

But as instruments have become more numerous on board and more complex, this wasn’t fast enough.

Nor was the one-way street of talkers and listeners in line with modern networking requirements.

What was needed was a protocol that allowed large quantities of data to flow back and forth.

The answer was NMEA 2000, which is based on the principles of a CAN bus — allowing devices to speak to each other without the need of a central computer to manage it.

N2K, as it is often abbreviated, runs at 250kb, which is 50 times faster than its predecessor.

An N2K network consists of a backbone cable running from one end to the other, into which instruments are plugged by means of a T-junction.

Plugs, wires and sockets are usually pre-moulded to eliminate the potential for poor connections.

Modernise your boat: Scenario 1 – New Plotter

Multifunction displays have developed as rapidly as mobile phones, and many no longer offer a legacy NMEA 0183 input.

Garmin’s displays will accept an N0183 signal via the audio port, using a special cable (£35); B&G’s Zeus displays have a similar work-around using an optional video/data cable.

The rest, including Raymarine’s Axiom displays, B&G’s Vulcan and Furuno’s Time Zero Touch range do not accept N0183 inputs at all.

In this case, you’ll need to buy a small black box converter that takes your old instrument data in at one end and converts it to N2K.

You’ll wire up this ‘gateway’ to the old instrument on one side and plug it in to the N2K network at the other.

Don’t be put off by the prospect of a ‘network’ on board when you modernise your boat.

Check out YBW’s guide to the best chartplotters available right now

All we’re talking about is a small backbone (simply a single central cable with readymade T-terminals and sections of multicore cable with pre-moulded plugs) into which each of your N2K devices are plugged.

It’s a bit like setting up a hose to water plants in your border – you won’t even need a screwdriver to assemble it.

Most marine electronics brands offer their own NMEA gateway.

B&G calls its one the AT10 (£110); Raymarine’s is made by Actisense, called the NGW-1-STNG (£165); and Furuno’s is the NMEA2K2.

There are also plenty of third-party ones, including Digital Yacht’s flexible iKonvert (£138).

If there’s only one N0183 instrument to connect up, then it’s simple.

But when you have several, the task can be harder.

Remember that in a NMEA 0183 system, you can’t just wire all the instruments together, because they don’t coordinate their data signals – it is the equivalent of trying to listen to several radio stations at once.

‘When joining together older NMEA 0183 systems to new NMEA 2000 systems, the most important step is to work out the best place to take the NMEA 0183 data from,’ says Paul Sumpner of Digital Yacht.

In the best-case scenario, the instruments will all belong to the same manufacturer’s range and can already speak to each other via a bus system, like Raymarine’s SeaTalk, Furuno’s NavNet and B&G’s Network.

It means you can take an N0183 output from just one of the instruments and get data from all of the instruments.

When I installed a new Raymarine MFD on my Sadler 34, I got wind, depth, speed and temperature all in one fell swoop by using a SeaTalk to N0183 converter cable from Digital Yacht (£150).

You could also use Raymarine’s own SeaTalk to SeaTalkNG converter, which costs £120 and plugs into your N2K network.

It could equally be an older plotter, GPS unit or an AIS receiver/transponder that is already acting as a multiplexer by gathering signals from several sources.

But if you have depth and speed transducers coupled with B&G wind and third-party AIS, then there are only two choices, according to Sumpner.

‘You can either fit a multiplexer to combine the NMEA 0183 data or fit multiple NMEA 0183 to NMEA 2000 converters.’

A multiplexer such as Actisense’s NDC-4 (£225) can accept N0183 data from up to five sources, which it stores and sequences to a single output.

Quark Elec produces one that will convert the data to N2K protocol and feed that into the network (QK-A034, £180).

However, some warn against the multiplexer solution.

‘They can be tricky to install and configure, plus you end up with one NMEA 2000 device that is putting lots of data on to the NMEA 2000 network,’ explains Sumpner.

‘The current preferred solution is to fit multiple NMEA 0183 to NMEA 2000 converters and have one for the AIS, one for instruments, one for GPS, and so on.

This way the NMEA 2000 network structure is more defined and devices can choose which data source to use, rather than be forced to use everything from the multiplexer.’

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Expert Tip

It is rare to damage a NMEA 0183 instrument by incorrectly wiring the data terminals.

However, make sure that you respect the polarity and always connect NMEA Out on the talker unit to NMEA In on the listener – never in to in!

Modernise you boat: Scenario 2 – New transducers and sensors

Not so long ago, most transducers and sensors used analogue signals to send their data to a dedicated display.

That option is still available through Nasa Marine’s budget range of instruments and through Raymarine’s current i60 display, although the preferred option is to run transducer signals into an iTC-5 black box that feeds it directly into the N2K network.

The same is true for other sensors and transducers.

If you wanted to install an ultrasonic speed sensor, such as Airmar’s UST800 (£1,135), it should fit the same through-hull as your traditional paddlewheel.

You then run the wire from the transducer into a black box which puts out the depth data in N2K format.

So you would need to create a small N2K network, even if the aim was simply to convert that data back into NMEA 0183 using a NMEA gateway.

AIS units are usually N2K, but often also offer a NMEA 0183 output.

Because of the volume of data, they use a faster version of NMEA 0183 that runs at 38,400 baud, not 4,800.

Make sure that any listeners attached to the AIS are either expecting the data at this rate, or put a multiplexer or buffer in-between the two — to ensure the whole network operates at 4,800 baud.

Expert Tip

Nasa’s anemometer generates NMEA 0183 data directly.

You can run its output straight to a NMEA multiplexer or another instrument with N0183 input.

From there, the wind data gets flashed around the network or sent to your smart device, according to your set-up.

Modernise your boat: Scenario 3 – New Display

A common addition to an older electronics network is a new repeater display, perhaps in the cockpit or at the chart table.

It is far cheaper than a more powerful MFD, but you will very likely face many of the same issues with connectivity.

New instrument displays like B&G’s Triton2 and Raymarine’s i70s will invariably use the more recent N2K standard, so to view speed or depth data from your old instruments you will need to convert it from N0183 to N2K, using one of the gateway devices mentioned in Scenario 1.

If there are multiple N0183 instruments, you may also need to add a multiplexer.

Once again, you are effectively creating a mini N2K network on your boat in order to use the display.

At its simplest, that means installing a short length of backbone with a T-piece node for the new display, another node bringing power in from the battery and a third node connecting the NMEA converter.

The benefit of this construction is that the network can easily be expanded in the future with new instruments.

Ben Holdsworth of marine electronics installer Greenham Regis says it is simple to build the network, but cautions against creating too many connections between different instrument groups.

‘Sometimes it’s easy to get yourself stuck in a data loop,’ he says.

‘For instance, if you have an N2K chartplotter and you want to delete a waypoint, that goes into the N2K network and across the converter to the 0183 network. But if you have SeaTalk connected as well, you can find that you never actually manage to delete that waypoint. By the time you’ve deleted it, it comes back onto the plotter via a different loop.’

This was the case in a recent job Greenham Regis did on a Swan, where the technicians found there simply wasn’t a sensible way to keep one of the old displays in the system.

If the prospect of a network makes you blanch, then you could consider another option.

French manufacturer NKE offers a Multigraphic display that can accept a single NMEA 0183 input.

Although these displays are designed to work with NKE’s own suite of more race-oriented sensors on their own proprietary TopLine bus, they will work perfectly well with older instruments.

It is not a cheap option, though, as these capable displays cost around €1,700.

If it is only simple data that you want to display, then Nasa Marine’s multifunction repeater (£289) could be the answer.

Note that it doesn’t let you customise pages or set alarms, just toggle through key navigation data.

Modernise your boat: Scenario 4 -Batteries, tanks and engines

Most sailors are well accustomed to the navigational data available from their instruments.

But recent developments have produced devices capable of generating a lot of data relating to critical onboard systems, including batteries, tanks and engines.

Imagine early warning of the engine overheating, water in the bilge rising or knowing exactly how much fuel is left, visible on your instruments?

This information could make the difference between calling out the lifeboat and making it safely home.

Bigger or more modern engines already produce digital data, which they typically share with the engine display panel.

Volvo Penta’s entire range even includes an N2K output, ready for hooking up to your instrument network.

But even a relatively simple engine like the Beta Marine 30 in my Sadler can be tapped for data.

As it is, the engine senses coolant temperature, oil pressure and revs which it displays on the tachometer, and in the form of alarms that are triggered when pressure drops or temperatures rise.

By replacing these simple on-off sensors with a resistive type sensor, it is possible to constantly measure these engine parameters.

Your engine manufacturer or dealer will be able to recommend sensors compatible with your specific model.

The challenge then is to turn the electrical signals from the senders into NMEA data.

For this, you need a special unit such as Actisense’s EMU (£387.61) or the Alba-Combi (€399).

Because they are designed to accept inputs from commonly used marine senders, there is little programming required.

You just need to connect up the wires from the oil and temperature sensors to the resistive inputs, then plug the other end of the unit into your N2K network.

As with previous scenarios, this network could be a new MFD or cockpit display, or it could be simple — just power, the engine monitor unit and then a NMEA WiFi gateway to get the data onto a phone (more below).

Another option would be to install a dedicated VeeThree display for engine data (£1,019.70).

This unit has a harness on the back that you connect up to the sender wires for older non-electronic engines, or to the J1939 CAN bus for newer engines.

With its N2K output, this device serves the double purpose of displaying your engine and tank data, then sharing it around the network.

Continues below…

Tank sensors work in much the same way as the engine senders.

If you have existing sensors, they are likely to be resistive types which can simply be wired up to the resistance terminals on your EMU or Alba Combi, although you will have to connect a laptop to the EMU in order to calibrate for your tank.

An alternative option is to use a specialist N2K tank adapter that allows you to plug your tank sensor directly into the N2K network.

Maretron offers one for a fairly steep £295. Yacht Devices charges £128 for its YDTA which will work with standard N2K fittings and with Raymarine’s SeaTalkNG. Maretron also offers an N2K monitor (£310) which can be used to show bilge pump use and could provide warning of a leak.

And Yacht Devices offers a range of handy N2K modules which simply plug into your network.

These include a digital barometer, humidity sensor and thermometer, as well as an exhaust temperature sensor (£125) that can measure up to 800°C.

Top NMEA mistakes

Here are the top mistakes to avoid when you modernise your boat

• Older AIS uses a faster version of NMEA 0183, operating at 38,400 baud. The only way to integrate it into a standard NMEA system is using a multiplexer.
• Connect NMEA Out on the talker unit to NMEA In on the listener.
• Garmin refers to NMEA negative as ‘battery negative’.
• You may need to adjust the settings of older NMEA instruments in order to switch on the NMEA 0183 output.
• N2K backbones must have a blanking plug to correctly terminate each end of the backbone cable, otherwise it won’t work.

Making use of the data

Now that you’re generating all this data, you’ll naturally want to get it onto a phone or tablet, where you can view it from anywhere on board.

The simplest solution if you have a modern multifunction display is to use the MFD’s built-in WiFi.

Check the maker’s instructions on how to switch on the WiFi function, which may require you to give the network a name and a password.

Then use your smart device to connect to that WiFi network, just as you would at home.

Remember that the phone or tablet won’t be able to access the internet through the WiFi connection with the MFD, unless you have separately set that up.

There are limitations to this, however, as Ben Holdsworth explains: ‘You can only use the manufacturer’s own app to view data,’ he says.

‘It can simply repeat the screen of the plotter — that’s all it really allows you to do, which is great, because you can create waypoints and turn the radar on and off. You can be tucked up in the saloon, keeping an eye on things.’

Garmin’s app is called ActiveCaptain, and includes everything from charting to autohelm control.

Raymarine has two apps that simply mirror the screen of the MFD, along with whatever data happens to be displayed, while its new RayControl app for tablets is more versatile.

B&G’s app, called Link, gives you control of most of your MFD’s functions from the phone or tablet.

If you really want to liberate your data, then you need a dedicated NMEA WiFi bridge.

‘It pulls the data off the system and broadcasts it out,’ says Holdsworth. ‘You open whatever app you want, to view the data.’

This is very different to your home router, so dispel any notions of using your old TalkTalk box.

Another reason to use this approach would be if your MFD uses its WiFi channel for connecting to a radar or camera.

There are many such WiFi devices available and if you have even a small N2K network then it is simple: just plug the WiFi gateway into your backbone and away it goes.

As power runs down the backbone, there is no need for a separate connection to the battery.

Products include Digital Yacht’s NavLink2 (£210) and Actisense’s W2K-1 (£185).

If your network runs on older NMEA 0183, then the installation can be a little more complex.

Just as in Scenario 1, you should first determine how many instruments need to get their data onto WiFi.

If it’s just one, then you’re in luck: simply wire in a NMEA to a WiFi gateway like Digital Yacht’s WLN10 Smart (£150).

More instruments mean more complexity and, if they don’t daisy-chain together (like Raymarine SeaTalk or B&G’s old Network units), then you will need a multiplexer to combine all the talkers’ outputs into one data stream.

This will then feed smoothly into the WiFi gateway, and thence, onto your phone or tablet.

Some products combine the multiplexer and WiFi function in one box, such as Quark-Elec’s QK-A031 (£100.80) which has inputs for three NMEA 0183 signals and one SeaTalk (Raymarine’s networking standard).

Digital Yacht produces another such unit called the WLN30 Smart (£210), which can take up to three different instrument inputs.

To view the data on your phone or tablet, you need a suitable app first.

There are literally hundreds to choose from, all with slightly different functions ranging from charting to data logging, as you can see from the short selection below.

If you specifically want an instrument-style display with none of the distraction of chart overlays and weather forecasts, NMEAremote (£14) looks good, supports a really wide range of NMEA sentences and can be heavily customised.

Once you’ve downloaded the app, simply connect your phone to your new WiFi network in the usual way, and away you go.

Note: Some WiFi bridges, including the Garmin GNT10, will only share data with their own proprietary apps.

Apps for instrument viewers

• NMEASail, £9.99
• Boat Instruments, £6.99
• iRegatta Pro, £19.99
• Marine Instrument Display, £8.99
• NMEAremote, £13.99
• SeaNav NP, £20.49

Setting alarms

The volume of data generated by a connected system can be overwhelming, so you need quick and easy ways of sifting it for information that is mission critical.

First of all, spend time with your new MFD or data display to customise the pages of information that you want to look at.

Set up a page that combines your new engine data, for example, alongside boat speed.

Another one could focus on wind angles and VMG, with a third with relevant GPS information — bearing and range to the next waypoint, plus boat speed and speed over the ground.

Next, set up alarms that will warn you of a potentially dangerous situation.

Every manufacturer does this in a slightly different way.

Almost every parameter can be given a trigger value, and you can then decide how that alarm is presented.

Does it sound an alert that you have to clear?

That could be useful for an elevated engine temperature, shallow depth or when the true wind gusts above your normal reefing point.

Perhaps just a warning on screen is necessary when the battery voltage drops below 50% or if you lose GPS connectivity for a second.

Apps can be just as good with alarms if you pick the right one.

NMEAremote, for instance, is very flexible and lets you determine exactly how it notifies you of any given situation.

Remember that electronics are no more than an aid to good seamanship.

After the novelty of your new MFD has subsided, there’s still the same need to carry a hand-bearing compass, keep an eye on fuel levels and conduct regular engine checks.

It’s also worth maintaining a secondary, separate GPS system — perhaps keeping your old unit and maintaining the old NMEA wiring in place, albeit unattached, so that you could quickly hook it up to your instruments in an emergency.

Modernise your boat: Case Study – Hunter Channel 245

After buying a used Hunter Channel 245, new owner Nick Meadow undertook an electronics upgrade with Garmin authorised installer Knight Marine in Port Solent.

The boat had an old Raymarine C80 chartplotter, a VHF and a small Raymarine i40 instrument for depth and speed.

He decided to install a new GPSmap 922, as it supported radar.

‘Plus, the Active Captain Helm feature would give me control of the screen via my smartphone,’ Meadow said.

This was paired with a GMR Fantom 18 radar. ‘While Garmin’s entry level GMR 18HD+ would have been enough for my needs, target tracking and power usage were of utmost importance,’ he continued.

‘So I chose the solid-state Fantom 18 for its Motionscope Doppler-effect target tracking, and its ability to lock-on to up to 20 MARPA targets to track their relative positions, giving closest point of approach and time to closest point of approach.’

Also on the list was a gWind wireless wind transducer, an AIS 800 black box unit and a Fusion Apollo for music and FM radio.

He kept the old i40 for speed and depth to avoid replacing the transducer.

‘We didn’t want to lift out the boat,’ said Paul Knight, MD of Knight Marine.

‘We bought a Seatalk to SeaTalk NG converter and put new N2K connectors to bridge it into the system.’

All the new wiring was hidden away.

‘We had to have the headlinings down at one point, and the floor up to hide the cables,’ Knight added.

‘In the heads, we had to make a box up to cover the back of the plotter displays, which we covered in vinyl.’

The owner also wanted the option to mount the chartplotter at the helm or on the companionway, so Knight created an ‘umbilical’ containing the network and power cables with plenty of give.

The radar was mounted on a tower on the transom, and is easily removed when not in use. www.knightmarine.co.uk

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