Yuku free message boards

more than likely your tanks are ok. So a good fuel cleaning service could do the trick. You could also burn your fuel on a long motor/sail To about 1/8 of a tank,replace your fuel, shock treat the fuel, new filters and see where you are from there. Fuel additives are great and can destroy the algae build ups , but the fuel filters really clog after a shock treatment of a fuel system so you might go through several filters.
I know of one fellow that cleaned his tanks as well as possible, still ended up replacing his tanks to cure the problem, although his tanks were 19 years old and stainless steel.
Also just as a thought, I have installed a water trap between the fuel vent and tank as this is a source of moisture entering the tank. Do not know if this helps but..................