Mercury - Portable Marine Fuel Tank with Fuel Demand Valve Red Blow-Molded Polyethylene 8M0045692. Overview. There's a certain comfort that comes from knowing your fuel system is dialed in before you ever leave the dock. When you're running a small outboard, you don't want to think about vapor lock, flimsy tanks, or guesswork. You just want steady fuel, clean starts, and the freedom to poke around shallow flats or cruise a quiet river without worry. That's exactly why this Mercury Marine part -