Skip to main content

Boat Monitoring System


Boat Oversight

In a world where you can track your friends’ locations in real time and stream yourself live on the internet, it should come as no surprise that you can also keep a close eye on your boat from the comfort of home. In fact, not only is there a plethora of options out there, but most of them go a lot further than simply telling you where your boat is. As for you Luddites who think this kind of thing is a bit much, be aware that many insurers offer a discount of up to 10 percent if you have a boat monitor, which means a basic system can even pay for itself in the end.

A Sentinel Marine monitor (left) and the readouts it produces

A Sentinel Marine monitor (left) and the readouts it produces

Raising the Alarm

At its simplest, a monitor is just a GPS tracker that relays your boat’s position to a computer, tablet or smartphone via a dedicated app. You can also pre-set a specific boundary—so-called geo-fencing—in which case it will warn you if your boat ever strays too far, much like an anchor alarm.

Most units raise an alarm via their local cellphone network and therefore only function in areas with reasonable coverage; even with a booster aboard, your range will be just a few miles. Many have built-in SIM cards with a set monthly subscription. Others allow you to choose your own. In either case, you should check the coverage for any areas you want to cruise. If you’re sailing off the beaten track, a more foolproof approach is to employ a monitor with satellite capabilities, like those more complex offerings from Nautic Alert and Yacht Sentinel. (Siren Marine also plans to launch a satellite service in late 2019.) Be warned, though, that this kind of performance comes at a price. Reckon $500 to $800 more for the hardware, plus a more costly service plan.

Navico’s GoFree Vessel ( also offers a satellite comms option; however, the system works slightly differently than most. Specifically, it harnesses the substantial on-board computing power of your existing B&G, Simrad or Lowrance instrumentation, piping in all sorts of telematics when the system is fired up and then acting as a basic tracker and alarm system after your multifunction display is turned off.

Of course, the real value of these kinds of systems emerges as you add extra elements. Indeed, in many ways, it is best to think of any base unit you may buy as simply a gateway to the internet to which you can hook up all sorts of useful extras. For example, dissuade ne’er-do-wells by switching on a relay that activates a siren or turns lights on and off as a handy deterrent. Similarly, make remote switching work for you by running the refrigerator or air-con through a relay, so you can have the boat ready upon your arrival.

Beyond that, the question is what stresses you most when you’re away from your boat. Is it the prospect of the bilge filling up with water? The shore-power connection tripping out and your batteries dying? Or do you stay awake at night imagining thieves helping themselves to your high-end electronics?

With respect to water ingress, nearly all units on the market support a simple on-off bilge level alarm that warns you if the boat begins filling up. Most also allow you to connect a bilge pump to a relay in order to switch it on remotely. Some will even monitor overall bilge pump activity for any unusual patterns.

This Nautic Alert system provides a wealth of information (left); The Nautic Alert wireless system is easily expandable (right).

This Nautic Alert system provides a wealth of information (left); The Nautic Alert wireless system is easily expandable (right).

Along these same lines, Nautic Alert’s X2 platform can be connected to a dedicated Nevata bilge controller that will monitor your water level to within 1/10th of an inch. You can also wire the Nevata to the pump directly to switch it on and off as necessary and even use it to diagnose detailed pump health and notify marina staff in the event of a critically high water level.

Nearly every unit mentioned below can also detect a loss of shore power, which is vital for ensuring your batteries stay in good shape at the dock. Most use the slightly agricultural expedient of a plug adapter that relays a 12V signal back to the base station, either wired or wirelessly, depending on the brand. However, while this works perfectly well, unless you have a dedicated power socket hidden away nearby it’s going to mean having a black box and possibly trailing wires out in the open.

Installing a Canadian-made BRNKL monitor alongside the companionway

Installing a Canadian-made BRNKL monitor alongside the companionway

Uninvited Guests

In terms of intruder detection, at its simplest, this will typically consist of a magnetic relay that is tripped when someone opens a door, triggering an alarm. (This works with hatches and washboards as well.)

Going up a step or two in terms of sophistication, pressure mats and even infrared (IR) laser entry detection capability are available as part of the Canadian designed BRNKL (pronounced “barnacle”) system. Beware, though: IR technology can only see in two-dimensions and is blind to the distance of a moving object. You could, therefore, find yourself inundated with alerts every time a boat passes and sets your towels or curtains, moving, depending on the intelligence of the algorithm behind the detector.

With this in mind, Nautic Alert offers a combined IR and microwave sensor that offers an ever greater degree of accuracy, making it suitable for use on deck as well as below. “Microwave technology can see how far away objects are, as well as how big they are,” explains Nick Velado, Nautic Alert’s product developer. “Together with a PIR (sensing) element that looks for thermal motion, it enables the detector to ignore small motion such as moving ropes, boomvangs, etc. It’s an extremely resilient intrusion solution for marine, and can be used to detect an approaching intruder before they board.”

Of course, for those in search of the ultimate in remote security, there is remote video, giving you eyes on whatever may have triggered the alarm. BRNKL, for example, not only includes a built-in camera, but you can add on a dedicated external camera unit as well. Similarly, Nautic Alert can be used to create an elaborate solution involving FLIR thermal imaging and up to 24 individual surveillance cameras, with the FLIR system automatically detecting the heat signature of any intruder and raising the alarm if someone breaks a specified perimeter around the boat. The system is also capable of transmitting video directly to your cellphone or computer and even allows you to direct the cameras. (Although for bandwidth reasons, this is usually only done on-demand, and via marina Wi-Fi or a dedicated cellular connection.)

The BRNKL app is one of many that allow you to check your boat using your smart phone

The BRNKL app is one of many that allow you to check your boat using your smart phone


In terms of setup, with simpler systems—especially those with wireless sensors—do-it-yourself installation is straightforward with a minimum of configuration required. Sam Handy of Siren Marine, for example, says of his MTC unit: “Most people could install it themselves, and around one-third of our customers do. The one thing we do recommend professional help with is if you’re doing the shorepower sensor, for obvious reasons.” Of course, with a more complex system, like the Nautic Alert, you will likely want to go with a professional as well (see “Case Study” below).

Finally, no matter what system you choose to go with, be aware that remote monitoring remains a young technology, so you can expect to see a whole lot more of it around in coming years. “Remote boat security is becoming very popular in the United States, especially in places like Florida where many boats and outboards get stolen all the time,” says Nautic Alert’s Verado.

“Consumers are starting to understand it,” agrees Handy. “And the marine industry is finally starting to embrace the technology.”


Yacht Sentinel YS6

The Yacht Sentinel YS6 wirelessly monitors position, battery and shore-power status, with extra sensors to detect motion in the boat, temperature, high bilge water and so on. Batteries should last about two years. Alerts are via 3G/4G. It can be expanded with a satellite comms module for around $880. If you go for the cell-enabled system, SIM card costs are included for the first two years. Annual subscription is $70 thereafter. The base unit is $700 with add-on sensors costing around $100.

Nautic Alert V-Tracker

Nautic Alert’s V-Tracker ($999) uses low-profile GPS and Iridium antennas to geo-fence within 250ft and alert you via satellite. An extra $520 buys you higher gain antennas with accuracy to 50ft. For daily reports, factor in a monthly subscription charge of $30. V-Tracker can also be expanded to include a remote-controlled engine kill switch, movement detectors, backup power input, a bilge float switch and an SOS button.

Nautic Alert X2

The X2 is Nautic Alert’s premium product and consists of an entire security and information platform. Information is marshalled, displayed and sent off via cellphone or satellite networks by the Insight header unit, including standard yacht telematics. Communicating wirelessly with Insight can be numerous Nevata bilge monitor and pump actuators, which give an incredibly detailed read-out of bilge water depth and pump diagnostics. The system’s XPulse unit adds a whole range of wired sensors, including four DC voltage monitors, shore power and four motion detectors. XPulse can be further expanded with the XPulse Plus for up to 32 wireless sensors. Not surprisingly this kind of functionality isn’t cheap, with the basic X2 alone going for around $2,500.


Supporting up to 12 wired sensors, the Swedish-built c-pod unit also allows you to switch equipment on or off using a relay. A basic package is $480 and includes a battery and position and magnetic intrusion alarms. In operation, the system draws just 25mA.

Siren Marine

The basic Siren Marine unit monitors battery, position, bilge pump and engine use. Various wireless/wired sensors are also available to further expand the system’s capabilities. Cost is $599. Iridium satellite connectivity is coming soon, as are yet more wireless sensors and video.


A bit different, this one, the MaxMon uses an Android phone as a transmitter, with its monitors connecting via a plug-in “Quatropus.” The system is a bit more DIY than most of the other units currently on the market, but can still manage remote switching, current and temperature monitoring and motion detection. Buy your own SIM card. The company’s two-sensor package goes for around $700.

GSM Commander

The GSM Commander is a flexible South African system designed for myriad uses, from agriculture to marine. At its heart is a GSM Commander Module, which uses a 3G signal and includes 12 inputs and 12 outputs. From there, your imagination is the only limit, with a range of different modules available, including all manner of actuators to turn things on and off. There’s even a remote pepper spray unit! The base unit costs around $400.

Sentinel Marine

The Sentinel Marine system is a smart-looking product with position and battery voltage monitoring standard, as well as NMEA 2000 data from your engine and instruments. From there it can be expanded to include intruder alert, bilge pump activity and temperature via a HUB that supports digital and analogue inputs. Sentinel doesn’t supply its own sensors, which means you have to buy them elsewhere. The unit’s BM40 monitor is $449. A yearly subscription costs $149.

Boat Command

This quality, low-cost unit covers the basics, including temperature, power, position and bilge pump run time. It can be also be expanded with various relays making remote switching possible. The base unit is $299. Sensors go for $29, and the subscription cost is $9/month.

Yacht Protector

This nicely designed system covers all the key security requirements using a battery of color-coded sensors. There are also plans to launch a climate-control module that will be able to switch heating and air-con on or off remotely. Cost is $999 for the base station and battery sensor and $195 for each additional sensor.


Designed by a Canadian sailor whose boat ran aground in a storm, the BRNKL uses wired sensors to keep an eye on nearly every element of a boat’s wellbeing. It comes with a built-in camera, and an additional external camera can be added for $115 extra. Other unique features include an impact meter that will tell you if something is awry during a storm. The BRNKL also measures heel and pitch and can provide basic engine running-time data. The base unit costs $750. Subscription costs are $20/month. 

Case-study: Passport 545

The owner of a brand-new luxury cruiser knew he was looking to spec a remote monitoring system when he commissioned his Passport 545. “I wanted to be able to monitor the security and key systems (batteries, bilges, etc.) of the boat wherever she happens to be when I’m not aboard,” he said. “At times, I will have to leave the boat in remote locations thousands of miles from me, and it gives me peace of mind to know that she is safe and sound.”

He asked Phil Mitchell of Annapolis-based Electronics Marine to spec out the installation for him based on a brief of safety and security. In total, the hardware from Nautic Alert came to $7,300, including two Nevata bilge monitors, wireless smoke and carbon monoxide detectors, plus night-vision 4K cameras, IR and microwave intruder detection. “We chose to install wireless security sensors, which made the Nautic Alert portion of the system reasonably non-invasive,” Mitchell said. “Panels were removed to route cabling for the GPS and Iridium antennas for the system.”

In fact, the most time-consuming part of the installation was making the custom mounts for the sensors around the boat and the antennas on the stern. The final part of the system was the shoreside connection. An Iridium unit is there as a backup, but the owner wanted to have a long-range Wi-Fi and cellular antennas as a cheaper, higher bandwidth coastal option. They turned to WaveWifi for this, installing its Rogue Pro Wi-Fi antenna and its MBR-550 cellular antenna with Wi-Fi hotspot built in. This technology costs a further $2,400, but gives internet access up to seven miles from a Wi-Fi access point. All the subscriptions are managed by Nearshore Networks, so the owner only receives a single monthly comms bill.

June 2019



Notice to Mariners: Flights of Fancy

The nature of sailboat racing is such that the bigger boats tend to get the lion’s share of attention. Recently, though, I’ve found myself especially impressed by what’s happening at the lighter end of the displacement spectrum. Those paying attention are aware there’s been a more


Sailing Scholarship for Teenage Girls

The Women’s Sailing Foundation is offering the Sue Corl Youth Sailing Scholarship to one teenage girl, aged 14-19 years old, who wants to expand her sailing experience and needs financial assistance in order to do so. Established in 2015, the scholarship allows the recipient to more


Celestial Navigation Part 4

In episode four of The Nav Station’s Celestial Navigation series, learn how to calculate your assumed position and the local hour angle using your Greenwich hour angle and dead reckoning position. Using examples in the western and eastern hemispheres, Andy Howe discusses why the more


Orca Encounters in Spain

The waters off the Atlantic coast of the southern Iberian Peninsula can be tough enough as it is, but in recent months resident pods of orcas have created a whole new kind of challenge, ramming boats and chewing off rudders. Though initially confined to smaller vessels, larger more


Video: Celestial Navigation Pt3

. In episode three of the Practical Celestial Navigation course, Andy Howe examines the theory behind celestial navigation, the celestial triangle and the celestial sphere, and why it is important to have a basic understanding of each. Topics introduced include zenith position, more


Sailing in the Time of Covid

In mid-August 2019, my wife, Terrie, and I laid up our Malö 46, Nada, in Falmouth, England, and flew home to Maine. We booked flights back to the UK for May 2020, anticipating a summer of cruising the Atlantic coasts of France and Spain. Then Covid struck. Remember that first more

Ulysse Nardin promo photo

The Ocean Race Names Official Timekeeper

With just under one year before the start of The 2022-23 Ocean Race, Swiss watch manufacturer Ulysse Nardin has been named the official timekeeper of the race. The Ocean Race, formerly known as the Volvo Ocean Race and before that the Whitbread Round the World Race, announced more

Arthur Daniel_RORC Maserati - RORC Transatlantic 2022 - Jan 15th -Social Media-4

Fast Finishes for the RORC Leaders

Over the weekend, the first finishers of the 2022 RORC Transat made landfall in Grenada, led by Giovanni Soldini’s Multi70 Maserati, which was awarded line honors with a corrected time of six days, 18 hours and 51 minutes. Maserati finished ahead of Peter Cunningham’s MOD70 more