How to Build a Gas Tank for a Boat
- 1). Pick the proper medium for the fuel container. Fiberglass fuel tanks are popular because they are lighter in weight than steel and last a long time. However, with the increased ethanol in gasoline, the use of fiberglass to build fuel tanks has diminished because the ethanol erodes the fiberglass and causes leaks. If you have a diesel gas engine, a fiberglass tank is still a good way to go. Fiberglass has the extra advantage of being able to mold to any configuration whereas stainless steel is somewhat restricted to square corners and rectangular shapes. However, for most recreational boats, stainless steel will be the better choice because they use gasoline.
- 2). Cut stainless steel sheet metal to the proper size for the fuel tank area in your boat with a circular saw or hacksaw with metal cutting blades.
- 3). Cut several inserts made of stainless steel sheeting to fit inside the tank as baffles to keep fuel more stable during movement. Baffles also provide extra bracing for larger fuel tanks.
- 4). Weld the edges of the tank together with a welding torch. Insert the baffles and weld them to the inside of the tank. As extra insurance, rivet the baffles to the sides of the tank with a rivet gun.
- 5). Cut out openings for the fuel sending unit, fill valve and vent. All fuel tanks must vent to the outside of the boat to relieve pressure and release volatile fumes.
- 6). Take your tank in to a local U.S. Coast Guard (USCG) station to be tested. The USCG enforces all Environmental Protection Agency laws for marine equipment. For most boats with the fuel tank installed behind the midsection in the aft compartment, these tests include a slosh test to be sure no fuel will spill from the containment system during fueling or motion, pressure tests (both static and impulse), and a fire test where the tank must be able to withstand open flames for at least two and a half minutes. If the tank passes, you will receive a certification label, and you can then install the tank in your boat. If you plan on installing the fuel tank ahead of the midsection of the boat, there will be more tests required.