Don't take it as gospel but I believe that motor should rev 46-4800 @ WOT. A 15 1/4 X 17P mirage should put you there.
It will definitely plain off faster but I am not sure about top speed.
I would think that boat should be in the 50 mph range though. That is if that motor isn't tired.
I have a 21ft wellcraft I use for fishing w/ a 170hp 4 cyl that is turning a 19p mirage and I get 40 mph out of that.
I would think being in the same size range (and most likely weight, about 3500 lbs) with almost 100 more hp you should be going a bit faster if it is running up to par.