OK, That's a Laser II prop. If you're serious about speed and want best performance from a merc prop, a Tempest or Fury will provide what you are looking for in the Merc line-up. There are some other options though. The Ranger hull you're running doesn't have much natural bow-lift and most Rangers require a serious bow-lifter to get the most from that hull. One option will be a Turbo Lightning. Another possible option is the Solas Scorpion, which I have tested and with some set-up tuning, the Scorpion will flat smoke a tempest if set up correctly and due to blade design, it requires 1" less pitch than equivalent Merc props. The Laser II is for very light, high HP boats-that's where it does it's best work. I think you would be cutting yourself short with a Laser II on a Ranger. Quicksilver has their equivalent props to the Merc Line in different names, although built in the same mold. As long as you have a water pressure gauge, you can get that engine at maximum height and really gain some speed with a high quality SS.
EDIT: Blade diameter is going to be only a function of blade design. when we get into this class of prop, seldom do they change diameter with pitch in the same model and the higher the diameter props can be run at higher engine heights-a plus when maximizing set-up.
