yamaha 250 ox66

Grady white 248 Yamaha ox66 250 Just got my prop refinished put it on no problem in the no wake zone Get up to 28 mph and all of a sudden slips out and sounds a little crunchy To me the engine sounds fine Fair to assume lower end? Haha

I need some help please. I have a 87 Grady Offshore Pro with full Grady drive bracket. The Boat has been repowered with a single 2001 yahama 250 ox66. I have a 14.5/ 17 pitch prop now and just not getting the job done. I know the prop is wrong but before I go try a hundred props I am hoping...