Man Overboard monitors the connection between each phone or watch and DataHub Pro. A lost connection does not always mean someone has fallen overboard. It can also be caused by Wi-Fi switching, a flat battery or loss of power to DataHub Pro.
Here is what to expect.
If a phone or watch leaves DataHub Pro Wi-Fi
When Monitoring is On, the device continuously communicates with DataHub Pro.
If that connection stops:
The disconnected device alerts first, prompting the user to check their Wi-Fi connection.
After approximately 30 seconds, the other crew receive an orange warning asking them to check that the person is onboard.
If the device remains disconnected, the full MOB Alert activates after approximately 60 seconds.
This gives someone who is safely onboard time to correct a simple Wi-Fi problem before the full MOB Alert is triggered.
If Internet connectivity is lost
Man Overboard does not require Internet for its core onboard monitoring. The onboard crew will always be alerted if someone leaves the boat.
If DataHub Pro Wi-Fi remains available but the Internet connection is lost:
Function | What happens? |
Device monitoring | ✅ Continues |
Onboard alerts | ✅ Continue |
NMEA 2000 MOB output | ✅ Continues |
Compatible chartplotter MOB position | ✅ Continues |
Email alerts | ❌ Cannot be sent |
SMS alerts | ❌ Cannot be sent |
If a phone or watch battery goes flat
A flat battery also stops the device from communicating with DataHub Pro.
DataHub Pro will therefore treat the device as disconnected and begin the normal warning and MOB escalation process.
Other connected crew devices can be alerted.
The device with the flat battery cannot alert its user.
If DataHub Pro and the required connections remain available, the normal MOB escalation can continue.
Keeping monitored devices charged is therefore an important part of using Man Overboard.
Clear an alert after a device battery goes flat
When the phone or watch is charged again, there are two ways to clear the resulting alert:
Acknowledge the alert in each app, then continue regular monitoring until the device has charged enough to reconnect. Turn Monitoring Off when you are ready to stop monitoring.
Reset the Man Overboard system from DataHub Pro. Open the DataHub, go to Services > Man Overboard > FLUSH MOB. This resets the Man Overboard system and clears the status of all connected devices.
For more information, see MOB - Acknowledge, recover and reset a Man Overboard alert.
If DataHub Pro loses power or Wi-Fi
If DataHub Pro loses power, every connected phone or watch loses its connection to the system.
The devices will alert locally and prompt users to check their Wi-Fi connection.
However, because DataHub Pro is no longer operating:
It cannot send MOB information onto NMEA 2000.
It cannot place a MOB position onto the chartplotter.
It cannot send email or SMS alerts.
From the phone or watch's perspective, it cannot tell whether the connection was lost because the person moved away from the boat or because DataHub Pro became unavailable.
A local warning on the device, therefore, does not mean that the complete MOB alert workflow has occurred.
If you receive an unexpected disconnection warning
If you are safely onboard:
Check that the device is connected to DataHub Pro Wi-Fi.
Check that DataHub Pro is powered and operating normally.
Reconnect the device if necessary.
If you are no longer on watch, turn Monitoring Off.
See MOB - Set up Wi-Fi for reliable monitoring for recommended Wi-Fi settings that help reduce unwanted disconnections.
IMPORTANT: Man Overboard is under active development. Alert timings and behaviour may be updated in later app and firmware revisions.
Next: Acknowledge, recover and reset an MOB Alert
Knowing that everyone is safe is different from simply hiding an alert on your device.
Next, learn how acknowledgement works, how devices recover after reconnecting and how to return Man Overboard to its normal monitoring state.