I have had this engine for 15 years, about 3000 hours, no big problem until this year on 10 week cruise in northwest waters. In order to start, I had to increase throttle progressively until at the end I had to push it all the way open, full throttle. It would start every time at that position and seem to run fine, throttle back immediately and idle at at 800 or so. If the engine was turned off thereafter, say from the slip to the fuel dock, it would restart again easily with only slight throttle, time it has for years. Next morning same problem. Also noticed white smoke while running under load, also new issue. If I throttle back a bit smoke would reduce but never go away completely. Usual running speed over the years has been 2400, any more would not increase boat speed much. I got nervous every and talked to a diesel mechanic in Everette WA. He OK to finish trip and return to home port (Olympia). He checked lift pump, said it was OK. Suggested I have the injector pump and injectors removed and serviced so they could be reset to factory specs. Also suggested replacing theexhaust elbow as a matter of course because of age of motor and have the heat exchanger cleaned. A friend, not a boat mechanic but many years in the truck diesel world, suggested that an air leak may be the issue because it sounds like the engine has lost prime while sitting overnight and thought maybe a faulty check valve. Most of what he said I did not understand. Any thoughts or first steps? Boat is on the hard and will not back in the water until spring. Thanks