As to cost of rebuild. We have a customer who was quoted 40K by Cummins to overhaul 1 of his 555 (smaller version of the 903) in a 50 foot Ocean Alexander. Cummins sold him 2 new 5.9 for 32k. After wiring, fuel, plumbing and labor he will be in for approx 70k and have 2 new engines. As to a 903 wouldn't have one.