You should be spinning that motor up to 5000 rpm. That is where the H.P. peak is. I picked up 14 mph on a heavy V hull at 6 psi boost so I would think 90 is not going to be a problem.
Do you have a GPS unit for speed? If not I would get one and have your passenger call out the speed numbers that way you can drive and trim up or down to get max speed.