Gas tank cleaning

[isby]

What is the best way to clean the gas tank of a boat that has been setting for about 10yr?

[bretticus]

If the fuel tanks are cast iron or steel, first you will have to make sure of the integrity of the tanks for rust and deterioration before you do any work to them.
If the tanks are not easily removable (most arent) then they have companies that do what is called "fuel polishing" to provide such a service. If they are easily removed then you can empty them, flush them out with a quality solvent, let them dry, and reinstall them.

[Ike]

Then pressure test the tank at three PSI to make sure it doesn'y have any pin holes. Once you hook the tank back up pressure test the fuel system as well.