I've been following your posts with a great deal of interest. Since I have the same model engine, my interest is magnified somewhat.
I do believe, however, that the culprit (if there is one) is something simple. (Like impeller shavings, etc.)
If there is no water in the bilge, leaks in the fuel tanks and the gages are all nominal, relax
! Keep your insurance up to date, life preservers at the ready, and enjoy the boat.
(Note: If this was my engine I would be tearing my hair* out!