Viking, from the looks of it there is a crack on the back side of the muffler and most likely on the radiused transition from the inlet end to the body (thinnest part). As easy as it appears to take out the muffler, me personally I would be all over it. Gotta love a DD to be able to work on it! There are two drains on my V drive mufflers (outboard/bottom) both sides but I have never gotten out more than teaspoon or 2 of water when I winterize. I would pull it and fix it myself with bondo and repaint it until I had another issue with it, which I doubt you ever would.