I replaced the float sensor last year and had to slide the tank as far as I could into the starboard lazarette. With the curve of the hull and only having an inch or two of room under the cockpit sole, I could barely get it over far enough to access the fill tube and sensor. I couldn't see any corrosion in the tank, but the float assembly was completely rusted out and I suspect is where the rust in the tank came from (picture below). I might be able to get the tank out if i removed the steering pedestal and ruder assembly, but can't do that in the water.
Interestingly, the gas in the tank and in the filter is yellow/orange and full of crud, but the gas in the carb float bowl comes out clear. The Perko filters must be working overtime.