To give a proper answer, let's get some proper questions asked. Diagnosis over the internet is not often easy.
So, let's hear exactly what your rig does WFO...full power, full trim, what's the exact speed and rpms?
At WFO, how is the lift? Where does the water break under the boat? How high is the roostertail? How stiff is the steering?
And the real question, 27 pitch WHAT? You might have a great prop, might have a turd, don't know.
Marble Falls/Seadrift TX