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 this out.
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 readings.
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.