Electronic Boat Engine Kill Switches

These engine cut-off devices, as the Coast Guard prefers to call them, can save lives.
MOB alert system
Most wireless engine cutoff switches allow you to leave the lanyard-activated switch that came with your boat in place and functional. Several states require its use if present; don’t knock it—it’ll shut down the boat if you’re thrown from the helm, but not from the boat. Courtesy Mercury Marine

An engine shut-off lanyard can save your life. That is, if you use it—and most boaters don’t. Even those who do generally only use it at the helm, and there are many other locations from which one can end up in the drink. Perhaps most at risk is the angler fishing solo.

A lifesaving option is a wireless engine cutoff device. Wearable fobs or “tags” communicate with a hub or host unit that sounds an alarm and shuts down the engine should the skipper fall overboard. A crewmember overboard fob is programmed to trigger just the alarm. Until then, anyone wearing a fob can move ­freely about the boat, without the short-leash hassle of a ­lanyard.

Read Next: A Cut-Off Switch Could Have Averted This Near Tragedy


There’s a range of systems available, from the electromechanical ­Autotether Marine cutoff device, to the wireless electrical Fell MOB+, to those that also log location through Bluetooth to guide you back to the MOB and even alert ­others, such as the ACR Overboard ­Location Alert System (OLAS) ­Guardian. And more are on the way.

Here’s what to look for in available wireless engine cutoff switches.

Quick Recovery


The Fell and ACR systems deactivate the engine shutdown in six or five seconds, respectively, so that the motor can be ­restarted to effect a rescue.

Pod and People

Autotether and Fell MOB+ can each monitor up to four fobs; the ACR OLAS Guardian can handle up to six Android- or eight iOS-linked tabs, and up to 15 with an extender.


There’s an App for That

The ACR OLAS works in conjunction with smartphone and tablet apps, providing onscreen direction to the MOB’s signal fob. (Autotether is self-contained.)

Designated Driver


Fobs can be programmed for operator (with cutoff and alarm) or passenger (alarm only) modes.

Drag-Along Protection

Fobs are triggered by distance or water immersion; an overboard and rigging-­tangled boater effects an alarm and, if designated as an ­operator, ­engine cutoff.


Mercury Marine has the 1st Mate system in the works, which will ­integrate into Merc-powered boats. We saw the stylish wearable during recent boat tests.

Big Boat?

Electronic cutoff switches are activated by distance from the module, and your boat may be longer than that. This problem is solved with an extender, such as that offered by ACR for boats 40 to 80 feet long.


Autotether Marine; $235, driver/ passenger sensor $90.25

Fell Marine MOB+; base pack $199.99, fobs/tags $19.99-$39.99

ACR OLAS Guardian; base $249.95, tag $79.95