We just had the same thing. Thought it was several things, head gasket etc. Ended up being bad injectors. Removed both, one totally clogged, and had them rebuilt with new tips. Just ran this past weekend for 4 hours and no white smoke or diesel film on the water when we came back to marina.
I will add that it was interesting getting one of them to seat back properly, but finally got it accomplished.
It was suggested to us by a mechanic that it is possible to add
fuel additive (10oz) and run for at least 1 hr at dock and see if it clears before removing the injectors. We had already pulled them when we were told.
However ours were so bad, I don't think it would have helped. Good Luck!