I could imagine a grain getting stuck in a seam and getting dislodged later.
Be sure to use a good fuel filter after this. I would think that even one grain of sand into your carb/fuel injection system would not be good.
I would do this only if the tank was an old vintage tank to keep a vintage look on an old 'show' boat.
Otherwise, for the cost of a new tank, I'd prefer to replace it.
Not to say that this type of yankee remedy wouldn't work.
