Mercury - Portable Fuel Tank 6.6 Gallon Fuel System UV-Protected Molded Construction 8M0045691. Overview. Every boater has had those days when the weather is perfect, the water is calm, and the only thing that matters is staying out just a little longer. A dependable portable fuel tank helps make that happen. This Mercury Marine part feels like one of those quiet companions you don't think about until you really need it-steady, sturdy, and ready to keep your day moving. With the 8M0045691 tank,