Larry Barth of Columbia, South Carolina, asks:
“For some reason the metal fuel tank feeding the Fischer Panda genset on my Hunter 41 now contains some water and other debris. How should I clean the tank? Would I be better off replacing the fuel tank with one made of plastic? Also, there is still about 10 gallons of diesel in the tank. How do I filter the fuel so I can use it?”
Nigel Calder replies:
It is common to find water and other sediments in fuel tanks, especially on older boats. Ideally, it should be possible to periodically pump out the tank and clean it. In reality very few tanks are designed this way. At the very least, your tank should have an access plate on top. You need to remove this and see if you can run a tube down to the bottom of the tank. If you can, use any pump that can tolerate diesel and pump out all the fuel. Then flush the tank with some of the diesel fuel, pump it out, and start again with a clean tank.
Many marinas have crews that provide fuel polishing services.
Essentially, these crews come in and remove the fuel, flush the tank until it is clean, then run the dirty fuel through filters before putting it back in the tank. If there is such a crew in your area, this is a very efficient way to proceed.
If there is no corrosion on the interior walls, its not worth replacing the tank. If there are signs of interior corrosion, I would seriously consider installing a plastic replacement tank certified to carry diesel fuel. On new construction projects, I always recommend that tanks be made of heavy-duty plastic to avoid future corrosion issues.