Engine Cut-Off Switch (Kill Switch) and Lanyard: The Law, Testing and Daily Use

Look at the helm (or the tiller handle and front of a tiller outboard). Note which type you have:

• Clip style: a horseshoe clip or key slides over or into the switch.
• Lanyard key: a plastic key that plugs into the switch.
• Wireless: a small fob on a wrist strap or clip, paired with a receiver at the helm.
• Personal watercraft: a lanyard key on the handlebar area; some brands use a coded key.

Write the brand and style in your BoatMend boat profile; you need it to buy the right spare.

If you're not sure when your boat was built, the Coast Guard's FAQ explains how to use the hull identification number (HIN) on the starboard side of the transom. In short: the last two characters are the model year. Model year 21 or later must have a switch; model year 19 or earlier is not required to; model year 20 depends on the certification date shown in characters 9 and 10. Either way, if a switch is fitted, use it.

Before each trip, look over the link:

• Coiled cord not cut, cracked, sun-rotted or stretched out.
• The snap hook or clip on the operator end opens and closes firmly.
• The switch-end clip or key is not cracked, bent or worn loose.
• The switch boot or button cover is not torn.

Replace a worn lanyard right away. They are inexpensive, and a stretched coil can let you move too far before it pulls free.

At the dock or on the trailer with water supply (muffs or a test tank, never run an outboard dry), start the engine at idle, in neutral. Then pull the lanyard clip off the switch. The engine should stop immediately. BoatUS recommends confirming the switch works at the start of each season, and outboard makers commonly call for this test before each use; check your owner's manual. If the engine keeps running, do not use the boat until the switch is repaired.

Reinstall the clip and restart. This confirms the switch resets properly and that you know how to restart quickly. On most boats, the engine will crank but not start, or won't crank at all, without the clip in place. A switch that lets the engine start with the clip removed may have been bypassed or have failed.

Wireless cut-offs need their own routine. Follow the maker's test procedure, which usually means confirming the fob is paired and that the engine stops when the fob is out of range or in the water. BoatUS reminds owners to refresh the batteries in fobs and wrist-worn devices at the start of the season. Some systems can register more than one fob, so passengers can be monitored too.

Clip the lanyard to something that stays on you: a life jacket D-ring or strap, a belt loop or a wrist strap. Clipping it to the steering wheel, the seat or a cup holder defeats the purpose. Attach it before you shift into gear, and leave it on until you're back to idle. If you hand the helm to someone else, hand them the lanyard too.

If the operator goes overboard wearing the lanyard, the engine stops, and the people still aboard need a clip to restart and go back. BoatUS's preseason checklist lists a spare engine cut-off lanyard among the safety items to have aboard.

• Buy a spare that matches your switch exactly. In BoatUS Foundation testing, one brand's key didn't fit any key in two "universal" key sets.
• Keep it somewhere every passenger can find without searching, and show them how to clip it in and start the engine.
• Store a second spare in your tackle box or ditch bag.

A clip that is missing, not fully seated or knocked slightly loose is a common reason a boat suddenly won't start or crank. Boating Magazine notes a key can look engaged but have slipped just enough to trigger the switch. BoatUS's outboard no-start checklist puts the cut-off cap right after the battery switch and neutral, and points out that on some setups the engine won't even crank without it. Before anything else, reseat the clip firmly, then work through the engine-won't-start guide.

The switch itself can also fail the other way: owners regularly find that a worn or corroded cut-off switch keeps the engine from starting even with the clip seated. If the engine is dead on an otherwise good battery and the clip is on, have the switch tested (step 10) rather than bypassing it.

If the engine doesn't stop when you pull the lanyard, or it cuts out over bumps with the clip in place, the switch or its wiring needs attention. Boating Magazine notes that aftermarket switches can be fitted to almost any engine and that the job is usually simple on modern ignitions, but wiring differs by engine and age (older engines with points ignition are more involved). Follow the kit's wiring diagram for your exact engine, or have a marine technician do it, then repeat the test in step 4.

A switch that works backward (the engine runs only with the clip off) was usually assembled or wired wrong, often after a replacement. Don't use the boat that way; have it corrected so it stops the engine when the clip comes off.