Mercury - Quickare Fuel Treatment Additive Fuel Care System Liquid Fuel Additive 8M0047930. Overview. If you've spent enough weekends on the water, you learn that most "engine problems" don't start on the water. They start in the fuel tank, quietly, between trips. A boat that ran perfect last month can suddenly idle rough, hesitate, or feel a little off-and it's often because today's gasoline just doesn't sit nicely, especially when ethanol is involved. That's why I keep a bottle of Mercury Quic