I double checked with my friend with the Baja. He's running 1.50:1 Bravo 1s, 4600 RPM, 23" pitch Mirage Plus and 68 MPH on the GPS.
Our air down here is hot and humid, so maybe it can be better where you are.
25s on our boat ran much like yours: no speed and low RPMs.
Spring for the 23s, but borrow a set first if you can.