Raymarine i70

Supervising the Iron Jib

Time for a technical post about some swish new gear I have just finished installing on Venilia. But first, some background.


A couple months ago, we took our home, comforts and all, over to Penguin Island…

I'll just pause for a moment to let the landlubbers in the audience reflect on that.

The day was magical. We had friends on board, warm sun, mirror flat seas and flying fish showing off for the amusement of all. With barely five knots of wind available, we set off early morning using the Iron Jib (engine) to lazily make our way north to the Island. We dropped the anchor a little after lunch time. Then came a quick snack, before Sheree and the kids jumped in the dinghy to head over to the beach for a swim and to look for the Island’s namesake inhabitants, fairy penguins. I remained on board, a little nervous still about my nascent anchoring skills.

Much fun was had over on the beach as I watched through the binoculars, including a little excitement and lessons learned by Sheree about beach landings in breaking waves (if you’re interested, the lesson learned is “don’t”). After that with all safely back on board, we decided it was time to lazily make our way back to the marina. By then, the wind had piped up a little to an ideal twelve knots, but of course, coming directly from where we needed to go, so we unfurled the Iron Jib again. A few hours into the trip, as I enjoyed some warm chocolate cake the kids baked for us down in the galley, it happened. A raw, blood curdling metal on metal screech and the engine stopped dead.


From my youthful eternal pursuit of squeezing ever more POWER from my moped’s fifty cc engine, I was no stranger to that metal on metal screech and instantly knew we had just seized the engine. This was bad. Very very bad.


The following morning, already looking through the online groups for a new engine, I ended up speaking with a chap very experienced with Gardner engines.  He told me this is not a K Mart unit and recommended I simply stop panicking, and go try to start her up again. Unbelievably, as soon as I pressed the starter button, she roared back to life with the steady rumble only a slow revving marine diesel can make. Clearly this engine was built back in the days where things were not considered disposable. No clunks, squeals or other vibrations, just a reassuring rumble. Many weeks of debugging followed with the local marine mechanic, oil analysis, oil change, coolant change, filter changes… nothing. All the tests came back showing a healthy engine. We simply do not know what happened. It could have been as simple as a rope wrapped around the propeller shaft. Maybe we will never know.

Fast Forward

On a sailing boat, the engine is an auxiliary, but it is critical and we need to be able to depend on it to get us in and out of the marina and also claw us off a lee shore should we ever get ourselves into trouble. Our engine having been designed and built in a different era, it has no electronic monitoring at all. If it goes to overheat or the oil pressure drops, unless someone is looking at the gauge at that very moment, we will not know about it until it is too late. That is unacceptable. In comes the Actisense EMU-1 (Engine Monitoring Unit) which is what this post is all about.

emu-angle-orangeActisense EMU-1

The Actisense EMU-1 is a specialised analogue to NMEA 2000 gateway. In English, that means it takes raw readings (voltage or pulses) from standard engine sensors and converts that information to specially formatted messages that are broadcast over the boat’s network. All the other devices connected to that network can then use these messages to display the readings or even set off alarms if a threshold is exceeded. So in short, if anything starts to look sub-optimal with the engine, the chart plotter and other instruments on the network will start beeping, display the problem and demand that we take action.

The EMU-1 is capable of monitoring six gauge sensors (current temperature, current pressure, tank levels, etc…), four alarms (temperature above N, pressure below N, etc…) and two tachometers (RPM). It can do this on up to two engines which is great, it will allow us to hook up the generator engine as well once we have that installed. For now, we are monitoring the following:

  • Coolant Temperature with Alarm
  • Oil Pressure with Alarm
  • Oil Temperature
  • Engine RPM


There really was not much to the installation of the EMU-1 itself. A couple screws, a connection to the NMEA 2000 network and a power hookup was all it took. Adding the sensors was a considerably trickier task. Not that wiring a sensor is difficult, but finding where to add that sensor on the engine and finding all the converters from British imperial threads to the modern American imperial threads of the sensors was a lot harder and took many weeks of frustration waiting for the eBay parcels to arrive. When said parcels arrived, the contents were not what I had ordered, so I ended up having to go to a local fabricator who made the pieces I needed in twenty minutes. Getting the RPM reading was also quite a job, since this is typically read by counting pulses output from the alternator’s AC tap, which our alternator did not have. We used this opportunity to also replace our old forty five amp alternator to a brand new ninety five amp unit that does include the required AC tap. Of course, with the alternator upgrade, all the old wiring was ripped out and replace with quality (expensive) new copper.


Everyone’s installation will be different using different sensors connected in different ways, therefore, before the EMU-1 can start sending messages to the network, it needs to be told which sensors it is connected to. This is done with the packaged toolkit software running on a computer connected to the NMEA 2000 network. A small gotcha here, I had to purchase the Actisense NGT-1 a USB gateway that allows me to hook the computer into the boat network. I think it would have been nice if Actisense had simply added a USB port directly to the EMU-1 for this purpose, but it’s a small gripe, since with the NGT-1, I can also now read all the information on the network on my computer and use many useful tools such as computer chart plotter software or instrument dashboards.


On a sail boat, the main engine remains a critical part of the boat that we must be able to rely upon. In our case, the EMU-1 was the ideal solution bringing critical information about our engine’s health onto the network and making it available from anywhere in the boat. Actisense’s support have been excellent and quick to respond to my queries and suggestions. The EMU-1 does exactly what is advertised on the box and I would recommend it for any boat whose engine does not have the option of connectivity to the NMEA network.


Mechanic, electrician, carpenter, plumber, upholsterer, rigger, author, painter, sailmaker, navigator, meteorologist and captain of the S.V. Venilia.

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