lower shaft repaired, now have RPM issue... thoughts?

Yamaha F90
I hit a shoal and bent the drive shaft, Marina repaired and now the boat RPM is much higher than normal! ie. full throttle/speed 6400 rpm now aprox 7500rpm.

My thoughts and tests:
- The New prop has the same stamp for size/pitch as the old one (could prop be stamped wrong?)
- hooked up another Tach and it showed RPM's match to eliminate faulty tach.
- could reassembly by mechanic accidentally put the wrong gears into the lower unit to throw the gear ratio off?

would anyone else have any suggestions on what to check? The marina has not given me any suggestions or options.

Thank you!

First off don't run7500rpms you will have pistons flying through the air , $$$$ Could be either wrong prop.or wrong gears. Was anything under cowl messed with?

I went out after the repair and noticed quickly that it was over revving... not running it like that, that was my indicator that something is not right...
-As far as I know there there was nothing messed with under the cowl... what there could be changed that I can check that would bring the RPM up?
-The Prop has the identical specs labeled on the previous prop.
-While changing the prop shaft, do they take it apart enough to remove the drive gears... could a different gear size fit where it would change my gear ratio? that is the only thing that I can make sense of... it's a big job just to check.

THanks

Hard to put different gears in there.----------Run back to the shop that did the work and ask for explanation on this.

Unlikely to be gears, but easy to check. Remove the spark plugs, put the engine into fwd gear and rotate the flywheel by hand whilst watching the prop. See how many turns of the flywheel are required for one turn of the prop after putting marks on both so you can measure the part turns (if any). That will tell you the gear ratio. Other way is to drop the lower unit and rotate the drive shaft by hand whilst in fwd gear.

It is much more likely to be the prop. Is the prop the same brand and model as previous? If it is a different brand or model you are probably just dealing with a prop that has more slip on your setup.