Mercury - Quicksilver Engine Starter Gear Reduction Series 12-Volt 8M6007399. Overview. When you work around heavy equipment or spend your days relying on compact tractors, skid loaders, or a small marine engine to get the job done, you quickly learn what matters most: the machine has to start - every single time. There's a certain comfort in turning the key and hearing that strong, confident spin that tells you your day is already off to a good start. The Quicksilver 8M6007399 is built for exac