Fish - You definitely need to get the RPM's up. Everything I've read about those engines says to prop that motor above 5500. NoBones and R.NAHIM have run the 19 pitch laser on there 200 mercs and switched back a 17 Mirage. Unfortunately Merc doesn't make a 17 pitch Laser II.
Fr. Frank (who used to run test boats for wellcraft) is running a Large Diameter 16 pitch powertech prop on his 150.
Both the mirage and the Powertech are real nice . . . if you have the $$$.
http://www.mercurymarine.com/props
http://www.ptprop.com/catalog/
Personally 45mph in my 20MA is about the max for my comfort level; However, if you wanted to get your RPM's the hard way, you might look into 2.0L mods on screamandfly or ByuBoyz. There are lots of mods that can be made to push the 2.0L merc well over 200hp.
www.byuboyz.com
www.screamandfly.com