Is this boat new to you? Did it do this before?
I did a quick google
on your engine and the cruising range RPM should be between 2600-3300 and the max rpm is 3600.
If you are only pulling 2250 at WOT (Wide open Throttle) I would suspect a restriction in the air inlet side - dirty filter, rag left in the air box or something.
Alternately you could have high drag on the boat - if she is sailing well you can probably rule
Finally if the prop has been changed from original I would say the pitch is too high.
As my grandma used to say, "Go back to the last thing you effed up."
We have similar hulls and power so my experience may help. I just repropped our boat. I did some speed studies today. 2-way average approximate GPS
2,000 = 4.8
2,300 = 5.2
2,500 = 5.6
3,000 = 6.0
We are probably going to run 2,300 for cruise
as we used to run 2,500 at 3.5 with the old prop and 2,500 is getting noisy. I think I could probably go a little higher on the pitch and may do that at the next haul out
. I'd love to get 6 knots at 2,300-2,400.