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Wireless MOB Systems

These new services can improve the success rate of rescues.

In man-overboard scenarios, time can be the difference between a happy outcome and a tragedy. The sooner passengers on board become aware of the situation, the sooner they can respond. In fact, statistics show that early notification is crucial to improving the odds of rescue. To increase early awareness, more boat owners are employing wireless man overboard systems. Today, there are systems to meet a variety of needs and budgets, from very affordable compact units that can be monitored from a cell phone to more sophisticated gear that can monitor up to 15 people. Here’s a look at a few of the newer systems that have come to market recently.

Weems & Plath’s CrewWatcher sends an alert when the wearer goes overboard.

Weems & Plath’s CrewWatcher sends an alert when the wearer goes overboard.

Weems & Plath’s CrewWatcher

 This is a cylindrical Bluetooth beacon that’s just 3 inches tall and 1.5 inches in diameter. It’s designed to attach to a PFD or the outside layer of clothing. If it, or the person wearing it, goes overboard, the beacon uses the CrewWatcher app (for iOS or Android) to send an alert to an onboard cellphone. The app can monitor up to five beacons, which can be attached to people, pets and even objects like a towed dinghy. The beacon will set off the MOB alarm if it goes out of range, or if the sensor on the bottom of the beacon detects it’s in water. Because of this sensor, Weems & Plath says you can also use the device as a bilge alarm.

If a beacon goes out of range, the app will show the last known position of the beacon. Once the beacon is detected again, the person monitoring the cell phone will see the distance to the beacon. Typical range in a clear area is about 98 feet, but that varies based on obstacles onboard. Each beacon has a non-replaceable battery that lasts 3 to 5 years, depending on usage. Price for each beacon is $89.


The system includes the ACR OLAS app (for iOS or Android) and an $85 watch-style tag or the $139 Float-On combination with floating flashlight and beacon. The latter is also a water-activated strobe that can be recharged via USB. The ACR app is similar to the CrewWatcher’s, but it also has a solo mode for those who travel alone. If a tag goes out of range and isn’t cancelled within a short delay period, an SMS message is sent to a predefined emergency contact with location and time of the event. This is a great way to inform someone on shore of a man overboard situation, provided the person who fell off the boat left the phone on the boat and that phone is in cell range.

A number of modules allow the user to expand the capabilities of this system. The USB-powered and portable Core module expands coverage from 6 to 15 devices and offers an 85 dB siren and red visual alarm. The 12-volt-powered Guardian offers the capabilities of the Core, plus an engine kill switch that will shut down the engine(s) in a man overboard event. The Extender module expands the range of the monitoring devices to support boats up to 100 feet. These modules should be available by the end of 2019.

Fell MOB+ 

This system isn’t tied to an app on a phone, but is installed in the dash of the boat. The module can pair with up to 20 tags and monitor four tags. One tag is designated as the vessel operator; if that tag goes overboard, the engine kill switch is activated and an alarm sounds. If any of the other three tags are activated, only the alarm is sounded. You can override the kill switch by pressing and holding the button on the dash module. A bundle with one tag and the dash module is $199; price for each additional tag is $40. A tag can be placed into a watch-band-style strap, attached by lanyard to a PFD or clothing, or clipped to a strap (or dog collar for those four-legged crewmembers). The tags have replaceable batteries that last for 300 hours.

Mercury Marine and Fell are working to integrate Mercury’s SmartCraft suite of digital instruments with Fell’s wireless technology. So far, they’ve announced SmartIgnition, a keyless ignition and anti-theft feature with MOB capabilities included, but more functions will come from this partnership. 


For More serious Cruising boats

For a long passage on open water, you may be better served by an AIS MOB Beacon or 406 MHz PLB. Unlike the Bluetooth beacons, these systems can tell you the actual location of the person in the water.

An AIS MOB beacon can range in price from $225 to $300 and will send a man overboard signal and the current position of that person to all AIS receivers within range of the beacon. The location is updated continuously and not restricted to point of loss, as is the case with the bluetooth beacons. SAR organizations monitoring the area and boats equipped with AIS receivers will be alerted to an emergency and can render assistance. Some of the AIS MOB beacons send a VHF DSC distress signal, so nearby boats with VHF radios can also receive a distress message.

PLBs (or personal locator beacons) operate using the same frequencies and technology as EPIRBs to notify rescue coordination centers of distress. This notification occurs via a 406 MHz link to the COSPAS/SARSAT constellation of satellites. PLBs equipped with a GPS receiver ($300 to $400) send a numeric identifier of the PLB and the location. That allows rescuers to retrieve personal information on the PLB’s owner and locate him or her. Both AIS MOB beacons and PLBs require the user to activate them, which means they’re not suitable for children. ­

This article originally appeared in the November 2019 issue.



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