What brand?
RPMs do not matter much anyway ,its the thrust ,during flight and throttle application.

Example.
I have an engine that will swing brand "A" 22x8 prop at 7600rpm producing 26 pounds thrust.
The same engine wil swing brand "B" 22x8 at 6700 rpm and deliver 32 pounds of thrust.
Same rated prop,different top rpm and much diffent results.

Static ground rpm mean little.
8k on your motor may not be top revs, but that prop may pull better than others at higher rpm.