Prop shaft HP vs Crankshaft HP may have something to do with it...
Just for comparison purposes, I have a Pursuit 2460 Denali. A bit lighter than your boat with less dead rise but maybe not that far off.
This year I upgraded my 5.7LXEFI Bravo III (250 HP at the shaft) to Vortec heads which made it into a 5.7LXEFI Gen+ (280 HP at the shaft) ie 30HP increase Both configurations call for WOT range of 4,400-4,800
before the upgrade 22P, WOT at 4,650 rpm 38 mph, 24 gph
after the upgrade 24P, WOT at 4,650 rpm, 41 mph, 25.46 gph
The motor before the upgrade with 24P only turned turned 4,200
This may not translate to your situation but I thought you might find it useful as a reference point.
Good luck!!!