You can seriously damage your engine adjusting here and there on those screws.

Sounds to me like some trash under a core plug on the carbs or some more trash entered carbs through hoses, fuel pump, etc. after your initial cleaning.

Pay close attention to screw-in jets and float valves during cleaning and inspection.

Trash, (ever so small) gets everywhere in a submerged engine:
you'll find some every week forever here and there.

The same trash and silt may also be stopping your timing {VIA spring action} from reaching full advance.

Check these few things and if no help; get back to me with more info.

O yeah, those mixture adjustments are for idle speed but can cause problems getting up on plane etc.
Too far out floods cylinders going to midrange.
Too far in (lean) starves engine on the way to mid range.
There's a fine line there, you'll find it.
Carbs should close completely and together [in sync].

Outboards don't run with any water in gas like a car will, zero; so check that close too.
GOOD LUCK

And I appreciated this note back.

Thanks Wayne,
Your answer is clear and easy to follow with directions a non mechanic could understand and use.