As Scott says, it may not be just the main engine that fails. I am also aware of boats with over 50,000 hours without failure (but these are very heavy duty marine engines in tugs). Our views are colored by our experience. On our last trip from the PNW to Florida I towed four boats along the way. Three of these had classical problems--the boats not been used much, there was sediment in the fuel tank, the boats had run out filters--and in several cases had run down the batteries to the point where the engine would not start. The fourth boat was off Panama and lost a tranmission. Certianly the fuel problems should have been prevented. The transmission is a different story. I have lost transmissions twice. Without a transmission you are out of luck. I have learned to repair that type of transmission (however you may not have the specific parts required and the tolerances are critical)--but there after carried a spare transmission. As Paul relates, large vessels are towed. To have a yacht towed by a commercial service would be very expensive. I have a friend who is a ships radio officer. Several times the ships engines have stopped at sea and a day or so taken to repair them. But the ships have engineers aboard and spares--many can decouple a cylinder so that the engine can run on reduced number of cylinders. Most recreational boats don't have this capablity. Bob Austin