Kill switch
An engine cut-off lanyard or wireless device that stops the engine instantly, killing the propeller if the driver is displaced or a rider is endangered.
Recreation
Kill switch is a term from limnology — the scientific study of inland waters. The detailed explanation below covers the definition, why the concept matters to lake water-quality interpretation, and how it relates to the A–F grade. Reading Kill switch alongside the A–F grade makes the grade easier to follow — each graded parameter maps onto an established limnological concept.
The per-lake pages on LakeQuality always show the specific Kill switch value for that lake, so you can move from the general concept to the specific lake without leaving the site.
What It Means for Your Lake
A kill switch (engine cut-off switch or ECOS) is a safety device that immediately shuts down the engine, and therefore the propeller. The classic version is a lanyard clipped to the driver that yanks the switch if the driver leaves the helm; wireless versions trigger if a person goes overboard. Federal law requires recreational boat operators to use engine cut-off devices in many situations. In wakesurfing the ability to instantly stop the prop is vital given how close the rider operates to the stern; cutting the engine the moment a rider is down in the fall zone prevents prop strikes.
Frequently Asked Questions
What is kill switch?
An engine cut-off lanyard or wireless device that stops the engine instantly, killing the propeller if the driver is displaced or a rider is endangered.
Why does kill switch matter for lake health?
A kill switch (engine cut-off switch or ECOS) is a safety device that immediately shuts down the engine, and therefore the propeller. The classic version is a lanyard clipped to the driver that yanks the switch if the driver leaves the helm; wireless versions trigger if a person goes overboard. Fede...
Related Terms
The set of practices that keep riders away from the spinning propeller, including using only inboard boats and shutting the engine off before anyone is near the stern.
The area of water immediately behind the boat near the propeller where a fallen rider is at greatest risk, prompting an immediate engine shutdown.
The person operating the boat, responsible for throttle, course, speed, and the rider's safety, working alongside a separate spotter.
Source: EPA National Aquatic Resource Surveys, 2026.