Well shux, i feel a bit dumb now

    Water in the fuel will ruin the tip of an injector. frequently a bad injector will let the fuel in before the piston is near the top and cause a knocking sound. Unburnt fuel makes a white/grey smoke.

     You can loosen the high pressure line at each injector [only do 1 at a time while it is running] and see what changes. When You get to one that doesn't make any difference in the running, that one is not firing. It might take a long time to make a difference in the smoke. Put rags around the injector to catch the fuel that comes out.

      Is Your oil level increasing? If it is, it is because unburned fuel is diluting the oil, so that would make it time to change oil regardless of hours.

       Black smoke is from partially burned fuel. This can come from an injector that does not break the fuel into a fine enough mist for proper combustion, or from a clogged air filter. The air filter issue normally does not cause a problem at idle [in the early stages] but showes up under load. In the latter stages, if it smokes at idle, You will not get full power, and get even more black smoke under load.

        Insufficient compression from a valve, cylinder, piston or ring [or other issue] problem can prevent the fuel from lighting off and burning properly. Does the engine crank at an even speed? Or does it have a cylinder that offeres less resistance as the piston is going up?

Hi , I have a classic 3d that started puffing black smoke under load one day. I talked to a reputable  diesel mechanic and he said it was probably not getting fuel, or the air intake was collapsed or plugged somewhat. After some investigation. I found a piece of cloth or rag on top of a little screen inside the top of the sediment bowl under the fuel tank. Cleaned the sceen, put it back together and problem solved. Sometimes something big can be rectified by some small thing . Hope your problem turns out to be fixable. I guess theres 2yr warranty on that machine. WS