The problem with portable fuel tanks over 12 gallons (aside from the fact that they're not legal to produce or sell) is that they're generally not baffled, and placing them above the boat's center of gravity can make the vessel unstable. Typically, large above-deck tanks are used only as a backup, to be transfered, in their entirety, to the main tank when it runs out. You wouldn't want a 20+ gallon tank going slack, with no baffles on a <20' boat...especially above the waterline. What kind of boat do you have that it has a 150hp motor and no integral fuel tank?
