Narrow boat fuel tanks are usually made of steel and are integral to the stern of the boat.

Filling is done from a deck level filling point contained by a small bund to prevent fuel spillage from entering the engine bay. A vent tube is situate on the top of the tank to prevent the build up of combustible gas.

The picture above shows a lockable fuel filler flap cleverly designed and fabricated to be integral to the curve of the stern. The tank vent tube in this example vents through the brass cap on the starboard mooring dolly.

A secondary outlet in the tank is often used to feed diesel fuel to central heating or stove systems. These will enter the tank higher than the engine fuel take off so that you run out of heating diesel before you run out of engine power!

It is also not unheard of for some narrowboat shell builders to incorporate a second fuel tank into the hull specifically for the storage of heating oil. The same considerations towards fuel spillage and venting apply.

Inside the engine compartment, your BSS examiner will check the condition of all fuel lines and will look for the presence of a fuel stop valve near the base of the tank.

On some traditional boats with centre engine bays, the main tank sometimes feeds what is known as a day tank. Often filled by a hand operated pump for authenticity, the day tank will provide enough diesel for a days cruising. Reflecting on days when vintage engines had no fuel lift pumps and had to rely on a gravity fed tank, day tanks are popular accessory.