The greatest risk of serious injury to a person in the water near a motorboat is being struck by a moving propeller.



Photo courtesy of the National Safe Boating CouncilA propeller is used to move a powerboat through the water (except for personal watercraft jet drive systems). Propellers can inflict severe, devastating injuries that result in death, loss of extremities, severe permanent deformity, disfigurement and/or disability. Every year people who recreate on and around boats are struck by the propeller of their boat or another boat.

A typical three-blade propeller running at 3,200 rpm can inflict 160 impacts in one second. A typical recreational propeller can travel from head to toe on an average person in less than one-tenth of a second. Most propeller accidents can be prevented!

Even propellers in neutral or at rest can cause serious injuries. Like carbon monoxide poisoning, the propeller is unseen and is extremely dangerous. It will be too late to avoid an accident once a person is caught in the pull or churn of the propeller blades. Boat operators can avoid injuries and death by informing their passengers of unsafe activities around the propeller, the proper use of safety equipment and by wearing an engine cut-off switch (ECOS).


Engine Cut-Off Switches (ECOS) were developed to help avoid propeller injuries on powerboats and to prevent runaway personal watercraft (PWC).  

In 2021, the U.S. Coast Guard announced a new federal law requiring the use of ECOS on recreational vessels less than 26 feet in length over 3 horsepower and equipped with an ECOS and the ECOS Link (ECOSL) to be worn by the operator. 

There are two exemptions for ECOS wear: if either the main helm of the vessel is installed within an enclosed cabin, or if the vessel does not have an engine cut-off switch and is not required to have one. (Generally, boats built prior to 2020)

Lanyard and wireless ECOS devices disengage the motor and prevent runaway vessels, collisions, and propeller injuries. Using the ECOS Link is required only when the vessel is operating on plane or above displacement speed.

In California, the law requires people operating a Personal Watercraft (PWC) equipped with a lanyard cutoff switch to attach the lanyard to their persons. Operating a PWC equipped with a self-circling device is prohibited if the device has been altered.

What boat operators can do to prevent propeller accidents:


  • Install/maintain propeller warning labels around back of the boat.
  • Establish routine and prevention strategies for safely starting the motor:
  • Check for people in the water near the boat, never start a boat with the engine in gear, never board or disembark when the engine is on or idling, be aware of congested areas and designated swimming zones.
  • Wear the engine cut-off switch to shut off the motor if you unexpectedly move away from the controls or fall overboard.
  • Assign a responsible adult to always report a head count to the operator before starting the motor and educate passengers about propeller safety.
  • When retrieving a person from the water (man overboard), turn the bow of the boat toward the person to keep the propeller away from that person.
  • To move the boat alongside a person in the water, as you approach, take the engine out of gear and turn off the engine at least a boat length before reaching the person in the water. Never reverse the boat to pick someone up out of the water. Go around again.
  • After the motor is off, throw a line or float to the person to pull them to the boat.
  • Never operate the boat under the influence of alcohol or drugs.

Passenger education to prevent propeller accidents

As the operator of your boat, it is your responsibility to properly inform your passengers about propeller dangers and how to avoid injury:

  • Call attention to the location of the propeller(s), discuss the dangers associated with them and point out the propeller warning labels on the boat.
  • Establish clear rules for swim platform use, boarding ladders, and seating.
  • Assign a passenger to keep watch around the propeller area of your boat when people are in the water and each time you are ready to start the motor.

Propeller safety equipment

A variety of safety devices are available to help prevent propeller strikes. Review all options to determine which preventive measures are best for your boat: 

  • Lanyard or wireless engine cut-off switches
  • Propeller guards
  • Ringed propellers
  • Propulsion alternatives
  • Interlocks
  • Sensors
  • Anti-feedback steering

Take Care - Be Prop Aware


Photos courtesy of the National Safe Boating Council and United States Coast Guard.