Man Overboard Location Alert Systems (OLAS): MOB Solved?

This guide to Overboard Location Alert Systems (OLAS) addresses your need to understand and select the best device to enhance safety during your boating adventures.

The fear of a man-overboard incident is real and can be overwhelming.

As someone who understands the thrill and risks of boating, I share your concern for safety on the water.

That’s why I’m committed to providing you with the best information on life-saving technologies like OLAS devices.

At a Glance:

1️⃣ Types of OLAS: There are various types of Overboard Location Alert Systems (OLAS), including manually activated systems, smartphone-based locators, and devices connected to a base station.

2️⃣ Selection Criteria: Detailed comparisons of OLAS devices based on cost, functionality, automatic vs manual activation, and maintenance requirements.

3️⃣ Safety Impact: The guide uses U.S. Coast Guard statistics to underscore the importance of OLAS devices in enhancing safety during boating and reducing man-overboard incidents.

📈 MOB Statistics

Carrying Man Overboard Systems is not a legal and enforceable requirement. But they are essential equipment for a safety-conscious boat captain.

The number of incidents that involve injury or death every year is substantial. The 2021 U.S. Coast Guard recreational boating statistics for man overboard incidents are listed below.

Accident EventAccidentsVesselsInjuriesDeaths
Person departed vessel1581717297
Person ejected from vessel18921915744

▶️ Functionality And Operation Of OLAS

There are several types of Man Overboard Systems:

Locator TypeActivation MethodTrigger ConditionAlert Displayed/Action Taken
Manual Location Activation (MFDs)Pressing “Man Overboard” button on MFDsManualLocation displayed in Chart plotter
Locator Beacon (Water Contact)Automatically activates upon contact with waterAutomaticeN/A
Individual Locator Device (Manual Activation)Manually activated by the victim (Man Overboard)ManualN/A
Locator Beacon (Base Station Connection Break)Automatically activates when the connection to the vessel’s base station is brokenConnection to base station is brokenN/A
Smartphone-Based Individual Locators (Connection Break)Sounds alarm and logs position when the connection is “broken”Connection to device is brokenAlerts all connected devices about the broken connection and logs the position
Video-Based Surveillance Systems (Large Vessels)Automatically detect Man Overboard emergenciesAutomaticFor large cruise liners and commercial vessels

⚙️ How An Overboard Location Alert System Works 

Alongside using a Man Overboard Location Alert System (OLAS), maintaining a proper lookout is vital for preventing accidents at sea. The following section explains how each of the systems works.

Man Overboard Button On The Vessels Multi-Function Device

These systems require a manual “man overboard” call. 

Crew or passengers should be trained to shout “Man Overboard on Starboard side/Portside” when an event happens.

On hearing this, the captain or helmsman presses a man overboard button on the system’s Multi-Function Display (MFD.)

While some systems use a dedicated MOB button, while others require a combination of buttons to be pressed.

The system marks the location of the event (when the button was pressed) on the systems chart plotter.

Some systems highlight the mark with a red cross displayed inside a circle, while others display the MOB location as a class B vessel.

Some systems will not immediately drop a pin on the event and require the action to be confirmed first.

This slows down the response times, making the location less accurate. In bad weather or high sea states, this delay could be the difference between a successful or unsuccessful rescue.

They are always available and need no setting up for each tripRequire manual activation. Someone must have seen the MOB event and shouted loudly enough to be heard.
The possibility of false alarms is virtually zero.Some systems require confirmation to be input before logging the location, which may result in delays.
Some systems require confirmation to be input before logging the location, which may result in delays.

Manually Activated Man Overboard Locator Device

These devices are attached to the occupants of the boat. 

The transmitter forms part of an Automatic Identification System (AIS).

If they fall into the water, they are manually activated by the following procedure:

  • A safety tab is slid off.
  • An arming cap is lifted up.
  • An antenna is deployed.

The mobile phone(s) then sounds an alarm and records the latitude and longitude of the incident using the phone or tablet’s GPS.

ACR OLAS then aids the crew with the MOB recovery, clearly directing them to the GPS location where the MOB occurred with clear visual signals and bearing data. ACR OLAS stores all location data and time of incident required by the rescue services.

When the device is activated, it sends a message on the AIS frequency (121.5 MHz)

The message transmitted includes a GPS position (normally accurate to 100 meters as well as a unique identity code identifying the unit.

These transmissions have a range of 5 miles. Most devices repeat the distress signal every minute for at least 24 hours.

Some of these devices can be equipped for manual or automated (immersion in water) activation.

The benefits of these systems are listed below.

They transmit on a radio frequency that has a 400-meter range (at least.)They are “vessel agnostic,” meaning they can be used on any vessel without having to first pair them.
They are “vessel agnostic,” meaning they can be used on any vessel without having to first pair them.
They have a longer transmission range than other MOB technologies.

Individual Locators Connected To A Base Station

These systems comprise of the following components.

  • An installed base station is used to connect to the locators.
  • Locators that can be carried (or attached to) each crew and passenger.

The individual locators are carried or attached to the vessel’s occupants. These can be carried in a pocket, as a watch, or attached to the lifejackets or PFDs (Personal Flotation Devices.)

While they are in range of the base station, a ‘virtual tether’ keeps the base station deactivates.

If the vessel occupant falls overboard, the tether is broken, and the system activates.

Depending on the model of equipment, activating the alert can result in the following actions.

1️⃣ Some of the equipment will immediately cut the power to the vessel’s engines (if it is a powered boat).

2️⃣ Sound an audible alarm.

3️⃣ Insert a location pin which can be accessed on the Multi-Function Devices display or transmit it to cell phones.

4️⃣ Some devices also automatically send a distress call on the AIS frequency 121.5 MHz. Even though this frequency is not monitored by rescue services, there are organizations and boats that are equipped with compatible receivers who will respond.

5️⃣ Some of these Man Overboard systems transmit alerts to nearby Class A and Class B AIS users over VHF frequencies. The alerts include the GPS coordinates and are repeated every minute for 24 hours.

There is no need to pair the devices.They are more expensive.
Ideally suited to vessels that carry a larger number of passengers.They are restricted to a specific vessel.

Smartphone-Based Individual Locators

These systems include individually worn (MOB) locators that are synched to one or more smartphones and tablets that have the app installed. 

If the transmitting device loses connection with the receivers, an alert is activated on the receivers within 2–8 seconds.

When this happens, the following steps are processed by the system:

1️⃣ An alert sounds on all of the receiving devices.

2️⃣ An alert flashes on the receiving devices’ screens.

3️⃣ The GPS location is immediately recorded on the receiving devices using their GPS location systems.

4️⃣ The app on the receiving devices provides a visual signal and bearing data back to the MOB incident.

5️⃣ If the sailor is boating alone, the system generates a series of SMS messages to the emergency contacts and provides the GPS coordinates.

If there are multiple cell phones or tablets synched with the transmitters, an alert will be created for each device.The system has to be paired with each cell phone or tablet.
Uses the GPS from the phone or tablet to provide the MOB location. It also uses this to provide steering instructions back to the victim.
The system can be used on any boat as long as the same cell phones or tablets are also carried.
They are relatively low-cost and expandable.

🔁 Comparison With EPIRB And PLB

Man Overboard systems are used to sound the alarm that someone has fallen overboard and enable a return to the incident location.

Systems that provide similar functions are EPIRBs and PLBs

Each system is designed for a different purpose, and there is little cross-over in functionality, as can be seen below.

MOB DevicePLB DeviceEPIRB Device
PurposeAlerts vessel of Man Overboard (MOB) event.Notifies emergency services of distress.Provides global location services for marine distress.
Response timeImmediate response, provides navigation data.Sends distress signal via satellite, longer response time.Sends distress signal via satellite, longer response time.
Location accuracyAccurate, max variance 100 meters.Accurate within 1 to 3 miles without internal GPS.Accurate within 1 to 3 miles without internal GPS.
PortabilityHighly portable, wearable.Portable, larger than MOB device.Bulky, suited for boat/raft.
Use environmentMarine and adjoining areas.Anywhere.Marine.
Range of operationUp to 400 meters (or 5 miles on 121.5 MHz).Worldwide.Worldwide.
Battery LifeUp to 24 hours.Up to 24 hours.Min. 48 hours.

🎯 Selecting The Best Overboard Location Alert System

When you are selecting an OLAS device, it is important to consider the following factors.

The Budget Available

The cost of the unit and whether it fits your budget. Also, remember that cheaper isn’t always better in the case of safety equipment.

The Technologies Used By Different Devices

The type of units:

  • Devices linked to the boats MFD.
  • Devices that transmit on 121.5 AIS system.
  • Devices linked to a base station
  • Devices that link to a smartphone app.

The ACR OLAS Tag is a Wearable Crew Tracker that integrates OLAS (Overboard Location Alert System) technology.

How The Device Functions

The different technologies (as discussed in this article) provide varying advantages and disadvantages.

How Many People The System Can Protect

Is the system designed to protect five or six passengers, or is designed for a large vessel with multiple occupants?

Whether The System Is Automatically Or Manually Activated

Does the system start transmitting automatically, or is it manually activated?

🪛 Installation And Maintenance Requirements

Most systems require minimal installation, while others do not require any.

Systems that use a base station require this to be installed in a location protected from the elements.

Cell phone-based systems require no installation other than the need to pair each MOB device to be synced with an app installed on the smartphones and tablets carried on the boat.

Each tag is supplied with a universal silicone wrist strap with a stainless steel buckle and a pre-installed CR2477 Battery (user replaceable).

All location data and time of the incident are recorded. Users can track up to six different OLAS Transmitters with one phone/tablet, and an unlimited number of phones/tablets can track each individual OLAS Transmitter.

Users can track up to 6 different OLAS Transmitters with 1 phone/tablet and each OLAS Transmitter can be tracked by an unlimited number of phones/tablets.

If you want to track more OLAS Transmitters, add the ACR CORE base station or Guardian Engine Kill Switch and scale your system to monitor up to 15 OLAS Transmitters.

Most systems require minimal maintenance other than to check that the batteries are in order and the following systems are working:

  • Battery functional tests – once a month
  • The systems transmission system (where appropriate) – twice a year

The AIS test should be carried out no more than three times a year.

💰 The Cost Of An Overboard Location Alert System

Man Overboard systems are available as per the following product prices

OLAS – Overboard Location Alert System$67.00 per watch
McMurdo FastFind Crew1$230.00
Ocean Signal MOB1 Man Overboard Locator Device$329.95
ACR ResQLink View GPS Personal Locator Beacon Survival Kit$418.95
ALERT Portable, DIY Man-Overboard Alarm System$1,795.00  

®️ The Process For Registering An Overboard Location Alert System

Other than equipment that transmits on 121.5, Man Overboard Location alert systems do not require registration. The MOB1 device can be registered at the following link.

🔑 Key Takeaways

The Man Overboard Location Alert System (OLAS) is one of many types of marine emergency beacons used for safety at sea.

1️⃣ Systems range from those that are manually operated, to devices that automatically alert the boat’s occupants of a man overboard event.

2️⃣ The prices range from $20.00 to almost $2,000.

3️⃣ Some systems use a Bluetooth connection to the cell phones carried on the boat.

4️⃣ Other systems use water-activated devices to start transmitting a distress signal on a frequency of 121.5 MHz.

I’m the founder and chief editor here at Sailing Savvy. I spent a decade working as a professional mariner and currently, I mix those experiences with digital publishing. Welcome, and I hope that we can be the hub you need for safe passage.