When my old wiring had finally been compromised, I was fogging the boat to put it away for the winter, everything was complete so I turned the key off - motor kept running. Took the key out - motor kept running. Played with the ignition for a few seconds - no luck, either. I had to climb in the boat and disconnect the fuel line from the tank. A shut-off would have been handy. I think, if you can do while it's all in progress, even if you don't use it often, someday it will come in handy and you'll be glad it's there.