Mike,
Sorry for your troubles.
This is a common problem, the internal tanks are usually way too big and you can never burn through a tank in a year. the fuel gets treated in the fall, a gallon or two are added in the spring, on and on. pretty soon the mean average age of the fuel in the tank is five years.
What I like to do is ditch the inboard tank completely and add a 3 gallon outboard tank complete with squeeze bulb. you do need to add a fuel return line by installing a brass barbed fitting from the hardware store or better yet another fuel quick disconnect. The squeeze bulb helps with bleeding the engine after filter changes etc. With this tank you can take it home with you to fill it, easily inspect the fuel and ditch any remaining fuel at the end of the year. The whole set up will run ya about $75.00. On a long voyage, just bring more tanks.
Mike
C227