"Absolutely"
I just recently did so when I enlarged my side plate from 3/8" NPT to 1/2" NPT.
I will confess I did the same as Al, and took the plate off and used my drill press & tapped the plate in a vice, so access and alignment were not factors.
However, I have also drilled the block in the boat to repair my failed 1/8" aft block drain and re-tap to 1/4". That was one of my first tasks when the old galvanized piece fell off the motor into my hand the first winter.
The 23/32" drill bit for the 1/2" tap cost 3 times what the tap cost!
