Mercury-Quicksilver 8M6007421 Engine Starter Yamaha Outboard Series 12-Volt 8M6007421. Overview. Every boater knows that moment when you turn the key and listen for the engine to come alive. It's a small thing, but it carries all the weight of the day-your plans, your crew, the water waiting just beyond the dock. A dependable starter isn't glamorous, but when it works exactly the way it should, you feel it. There's a kind of quiet confidence that settles in, the kind that tells you you'll be on