Old crusty gas in the bottom of a steel OMC tank. Anyone know of a good way to clean it out. Its gummy and kind of soft. Tried to leave a mix of fresh gas and oil mix in it over the winter and that seemed to soften it a bit but still stuck in a lot of it. Tank is in good shape other than that as in no rust inside or out. Is there something that would dissolve it? Thinking a can of Sea Foam or maybe some of that stuff used to soak carb in?