All i have is , are you reading off the pitot or gps ? Maybe something got whacked and your losing a pound or 2 of water pressure now. Or your trim sensitive and the limit isnt set where it was .

If you are running same prop, same drive ratio, and are still running same rpm, I'd think it's a setup or trim issue. Not seeing how hp will come into play here

did the bottom of the boat get damaged in any way? If no damage to the boat then the prop did get hit. This is a single engine boat? if not is the drive alignment correct.

There was no damage to the hull at all. I did, however have the bottom of the boat buffed and waxed to help keep the river water stains off. I know that's not optimal for speed, but I wouldn't think it would cost 6mph.

As far as the trim, I can still trim it up enough to blow out the prop just like I could before.

It is a single engine boat, GPS speedometer

Joe, were you running the boat in heat? You were at desert storm correct?

The wrong wax will slow a boat a lot more than you would think. Wax is the wrong thing to put on the bottom of your boat. Wet sand for speed. They used to make a bottom coating that when I used it I would see about 3 MPH gain BUT they stopped making it because it was made with a chemical that was banned in the USA. ( OZONE depleting )

It was only around 90deg. If it is the wax causing it, I guess it will get back to normal after a few more times on the water. No way I would wet sand. The stains in the mud holes that I boat in would never come off.

If you hit something hard enough to trash the outdrive and a transom assembly and you still believe the prop emerged
unscathed you may want to rethink it.

No way a cursory visual inspection by you will find slightly bent ears on the prop. Have it scanned to truly know.
You can perform a pointer test yourself but it requires a bit of set up.