Aluminium marine gas tanks do not last forever since they endure corrosion and exposure to the environment like any other boat component. However, aluminium has its advantages over other materials used for gas storage on marine vessels, chiefly that it combats corrosion better and weighs less than other heavier metals, including some fibreglass tanks. Fuel leakage from an aluminium tank requires an immediate response, since liquid gas and fumes constitute a danger to on-board passengers. Finding and repairing a leak in an aluminium tank need not be difficult and only requires some practical steps and basic tools.
- Skill level:
Things you need
- Siphon (hand pump)
- Gas cans
- Socket set
- Ratchet wrench
- Water source (high pressure)
- Air compressor
- Drill motor
- Cone bit
- Sandpaper (400 grit)
- Safety goggles
- Particle mask
- Marine weld epoxy
- Plastic cup
- Putty knife
Trailer the boat to a convenient work location and park the tow vehicle with the emergency brake set. Remove the lanyard key from the ignition. Disconnect the negative battery cable with a socket. Shut off the main fuel feed valve at the tank and at the engine. Use a screwdriver to loosen the gas intake hose clamp and pull the hose from the gas tank neck.
Disconnect the fuel discharge line that goes to the fuel pump with a screwdriver. If equipped with a vent hose, unclasp the hose end or loosen the clamp with a screwdriver. Disconnect the tank sensor wire, if so equipped.
Place a siphon hose in the gas intake inlet and pump out the gas into a certified container. Remove as much gas as possible. Use a socket and wrench to remove the strap or bracket bolts that hold your gas tank to the stringers or bottom deck. Be careful not to tear any rubber mounts or insulation under the tank.
Use an assistant to help you remove the tank from the boat and set it on end over a suitable drainage area. Drain any remaining fuel from the tank into a certified container.
Use a high pressure water hose to flush the inside of the gas tank, removing all gas traces. Use a compressor air nozzle to force-blast all moisture from the tank. Set the tank on end, allowing it to drain and air dry completely. Place the tank in a position to work on the damaged area.
Chalk an outline of the crack or corroded area, allowing at least a three-inch overlap. For a small crack or hole, use a drill and conical bit to grind a bevel in the crack, or open up the hole to produce new metal on the sides of the hole.
Use 400-grit sandpaper to sand over the crack area or hole, overlapping the area on all sides by 3 inches. For a corrosion spot, sand over the entire corroded area down to bare metal and overlap on all side for 3 inches. Don gloves, a particle mask and goggles. Wipe the area down several times with acetone and a rag. Wipe dry with a rag.
Mix the contents of the marine epoxy weld according to directions. Mix the epoxy agent with the hardener solution in a cup and stir vigorously. Apply the epoxy weld compound over the crack or damaged area with a putty knife, using pressure to shove it down into the crack or hole.
Use stiff pressure to force the epoxy compound inside the tank. Build up a several layers of epoxy weld over the damaged area, extending out to your chalk marks. Let the epoxy weld dry and cure according to directions.
Have your assistant help you place the tank back in the boat. Align the straps or brackets and insert the mounting bolts. Tighten the bolts with a socket. Reconnect the main fuel intake hose and tighten the hose clamp with a screwdriver.
Hook up the discharge fuel line and tighten the clamp with a screwdriver. Replace the fuel vent hose and snap the clasp or tighten the clamp with a screwdriver. Reconnect the fuel tank sensor wire, if you have removed one.
Refill your gas tank with the reclaimed gas from your containers. Check for leaks.
Tips and warnings
- You can repair the gas tank with HTS brazing rod, using a torch to heat up the aluminium surface until the rod flows and fills in the cracks. The surface preparation and treatment is identical to the cold epoxy weld procedure. You will use flux to prep the metal before welding and a slag hammer to knock off bits of residue.
- No smoking or ignition sources should be allowed near the boat or gas tank while performing this procedure. Even slight fumes can ignite, causing injury.
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