Suggestions on Gas Removal From Boat Gas Tank

There comes a time when a boat fuel tank must be drained of all fuel, for a cleaning procedure or as a method to exchange old contaminated gas for a fresher blend. Boat tanks, because of constant vibration, can also fill up with rust, which can lay as sediment at the bottom of tank. Some tanks must be cleaned in order to remove all traces of water, sludge and varnish. Whatever the reason, a boat owner has a few options when it comes to draining his boat tank of fuel.

Outboard Portable Tanks

An easy procedure for removing fuel from an outboard tank requires running the motor until a substantial amount of fuel has been consumed. If the tank holds a regulation 5, 10 or 15 gallons, the next step requires removing the intake gas line, using pliers, a screwdriver or pulling the quick-release, and then pulling the tank out of the boat. The remaining fuel can then be manually emptied into a certified container. The procedure will work for a larger aluminum tank, held to the bilge by straps. After the strap bolts have been removed with a socket, the tank can be manually emptied by two persons.

Shake-Type Siphon

A boat owner can use a shake-type hose siphon on a portable or inboard tank. One end of the siphon hose is placed inside a container large enough to accept the discharged fuel. The owner removes the tank inlet cap and snakes the other end of the hose into the tank, with the siphon valve just above the bottom of the tank. The hose inside the tank has a one-way pressured-induced flapper valve, that when vertically pulled up and down (shook), the hose draws fuel, creating a prime suction. Once sufficient pressure has been reached, the fuel will automatically siphon into the container.

Air Compressor Method

An air compressor works well for larger and heavier tanks. Remove the valve connection on the output end of a compressor hose and wrap a long rag around the end of it. Use a screwdriver or pliers to remove the tank line attached to the carburetor side, and place the line inside a large container. Remove the gas tank cap and wedge the compressor hose (with wrapped rag) into the cap opening, forming a tight seal. Turn on the compressor and let the pressure inside the tank force fuel through the hose into the container. This will remove nearly all of fuel from the tank.

Wet Vacuum Method

To insure that all fuel has been removed from the tank, a wet-vac hose is placed down inside the fuel cap tank opening. The wet-vac machine is then turned on. The residual fuel will be vacuumed up and collected in the wet-vac canister.

Mobile Fuel Evacuation

For very large commercial tanks, including diesel tanks used on large vessels and trawlers, the owner can contact a mobile service that will arrive on site with a commercial pump and filtering system. The procedure is known as "polishing." The service will remove all fuel, including bottom sediment and dispose of it, or recycle it for the customer. The service provides a safe and thorough fuel removal, using only a minimum amount of downtime for the customer.

Primary Bulb Method

A boat owner can disconnect the fuel line at the primary fuel filter side and place the hose into a jerrycan (container). The jerrycan should be placed below the elevation of the fuel tank, if possible. Squeezing the primary bulb will prime the line and discharge fuel into the jerrycan. After a while, gravity and the siphon flow will start a full discharge and drain the tank. Any remaining fuel residue can be picked up with the wet-vac suction method.