Sponge retrieval.
John, I wonder what would happen if you used an electric oil changing pump with two hoses attached to it, one intake, one discharge? I envision pulling fuel into the pump from just below the surface and returning it at the bottom of the tank. My thoughts run along the lines of starting a current that would eventually float the sponge to within reach of the access port. Tim's comment about adding one to his tank reminds me of an experience I had with the 39 gallon diesel tank in our boat. The factory had fitted a white plastic one (5-6" diameter maybe) that was all cracked and patched with Permatex. West Marine carried the identical brand so I fitted a new one. Within a year or so that one had developed the same cracks. A call to the maker revealed that it was impervious to almost anything except diesel and presumably gasoline. The final fix was that I ordered a slightly larger one from Bomar made of cast aluminum with a Nitrile sealing gasket, see it here:
http://store.hamiltonmarine.com/browse.cfm/4,2554.html I simply enlarged the hole slightly in the tank, vacuumed up all the aluminum chips (that's where the recirculating idea comes from) and installed the new one, problem solved. I might add that I did this with a full tank of fuel, allowing the aluminum chips to fall to the bottom. I bought a Reverso oil change pump that I later attached to the crankcase of my Yanmar and along with an in-line ITT filter screen and two pair of women's Nylon peds clamped to the end of the return hose, vacuumed up every last chip. I know this to be true because the fresh fuel was clear enough to see every speck of debris on the bottom. Regards, Glyn Judson, E31 hull #55, Marina del Rey, CA