Permanent fuel tanks are marine fuel tanks that are installed permanently on a boat. Inboard and stern drive boats usually have permanent fuel tanks mounted underneath the deck. Most permanent fuel tanks hold gasoline and are made of polyethylene plastic or aluminum.
Permanent fuel tanks usually hold more fuel than portable fuel tanks. They also experience less wear and tear from exposure to the sun and cold, and they do not have to be taken off the boat for refueling. They are less likely to develop leaks because they don't have to be attached and detached from the boat motor as frequently as portable fuel tanks are.
On the other hand, permanent fuel tanks require direct fueling at the site of the boat, which is not always convenient and creates the additional risk of dropping the gas cap into the water. In contrast, portable tanks are easy to carry to a gas station for fueling, and filling up more than one portable fuel tank provides extra fueling power for long trips.
Another disadvantage of permanent tanks is their less accessible location. This makes it easy for boat owners to overlook the fuel system when performing routine maintenance on the boat.