I used to know what I was doing 25 years ago when I had my last boat but am closer to a novice now. That might explain why I ran out of fuel, sort of. Left Annapolis on Saturday heading 40 miles up the bay with my recently purchased Tayana 42. New filters, clean fuel, half a tank in each of the 2 tanks. Sailed a good bit but with the wind on the nose needed to do a good bit of motoring for time constraint reasons. Somewhere along the way the engine does a slow sputter and dies. Check the fuel tanks. Port side empty, starboard side full. What, it was only half full when I left! Light bulb goes off. For some reason the previous owner had the port side return valved to the starboard tank! Now why would he do that! What I did wrong: not check the valve alighnment. What I did right, not much. What the heck, we all had a good time anyway.