Much of the time I'm the only adult aboard my boat. I either single-hand or cruise with my young daughters. And one particular risk troubles me more than all the others combined: What if I fall overboard?
Alarms can alert parents if children go over – and some can stop the boat if it is a parent who winds up wet. There are several products designed to raise the alarm and assist with the recovery of crew overboard. To be clear, these systems are distinct from distress radio beacons such as EPIRBs and Personal Locater Beacons (PLBs), which help search-and-rescue authorities locate boats and people in distress.
Instead, man-overboard (MOB) alarms alert the boat's crew that one of their crewmates has fallen off the vessel. It works like this: A transmitter is attached to each crewmember – usually a small tag, about the size of a car remote – and a receiver is installed aboard the vessel. The receiver sounds an alarm automatically when a crewmember falls overboard. Most transmitters have a button or switch that allows crew members to manually activate the alarm as well.
Most receivers can also trigger the MOB function on a GPS or chart plotter, generating a waypoint using the vessel's position at the splash point. Many can disengage the vessel's engines or activate other MOB-recovery gear. Some systems can even provide real-time direction finding to help recover the crewmate in the water.
Overboard preparation is a priority for all experienced boaters, particularly those who venture further from shore. MOB alarms have gained in popularity in recent years, with roughly a dozen companies – including Raymarine, Mobilarm and Autotether – adding to the arsenal of modern safety gear now available.
Although the best advice remains "Don't fall off the boat," the fact is that falls overboard, along with capsizes, account for the biggest share of boating fatalities reported to the U.S. Coast Guard. Ninety percent of drowning victims are found without personal flotation devices, or PFDs. So wear a lifejacket when onboard. My children even wear them on the dock.
Once a crewmember has fallen into the water – hopefully with a PFD on – the top priority is getting him or her back aboard. The sooner the engines can be stopped, or a GPS waypoint set, the better. Ideally, falling in the water would trigger an audible alarm, set a GPS man-overboard (MOB) waypoint and stop the boat.
The MOB alarm systems currently available use one of two basic operating principles. It is important to understand the distinction between the two to select the right one for you.
PROACTIVE OR REACTIVE
Proactive or proximity systems are activated when a constant signal produced by the transmitter, worn by a crewmember, is interrupted. Signal interruption might occur due to an increase in the range between the transmitter and the receiver, as when a crewmember falls overboard. However, an interruption could also occur if the transmitter were unable to transmit due to radio-frequency interference from other equipment, a discharged battery or damage to the transmitter itself. False alarms are more likely with these systems because any disruption in the signal triggers an alarm.
Reactive systems are activated when the transmitter, worn by the crew, is immersed in water. However, if the transmitter or its battery fails, no alarm is triggered aboard the vessel, so it's possible to experience a situation in which somebody has fallen in the water but no alarm is triggered. Transmitters remain off most of the time, so there is little drain on their batteries. Some reactive systems use a direction-finding antenna aboard the vessel to help the crew locate the MOB.
So which is better?
