Mercury - Moving Prop Alert Light System (Oval) Non-SmartCraft Safety Kit 8M0109508. Overview. A spinning propeller can be difficult to see in the water, especially around swimmers or people reboarding the boat. The Mercury 8M0109508 Non-SmartCraft Moving Prop Alert Light System helps make that danger unmistakably clear. This oval-style kit uses two bright LED smart lights connected to a control module that monitors engine status. When the engine is running and the prop is turning, the lights fl