I think I had my turbo rebuilt twice during the 5500 hour lifespan; once @ 2700 and the other around 42-4400. Not being able to reach 4000 W.O.T and seeing a little black smoke tint rising above the boat wake on flat glassy days were the telltale signs. I would also grab the turbo vane and check for sideplay and freedom of spin each time I changed the air filter. I think I had the injection pump rebuilt 3 times and we went through the injectors 4 times,changed the elbow once, intercooler twice, and heat exchanger once, replaced raw water pump complete once, probably 8 or so impellers; replaced the recirculating pump once, alternator 4 or 5 times and 2 starters.