When you take-off, (and land), the prop should be set to fine. This puts less strain on the engine as the propellor spins faster. (Like first gear on a car).
Once in the cruise adjust the prop to coarse pitch. This takes bigger bites out of the air and the prop spins slower. (Like top gear on a car).
Note that as you increase the pitch the revs on the tachometer will decrease, adjust it 'till the needle in just inside the green arc for maximium efficiency.
I love playing tunes on the propellor control...

...!
(Also try reducing the mixture control slightly, (weaker), as well. This will also reduce fuel consumption, and increase efficiency).
When you have done this, and trimmed the aircraft correctly, you will notice a significant increase in air speed...

...!
NOTE:...Don't forget to put the prop control to fine pitch and the mixture control to full rich prior to landing, just in case you need full power for a "go around", or "missed approach"...

...!!
...and make sure "carburettor heat" is off..!
Cheers all...

...!
Paul.
(England).
Win 8.1 64-bit. DX11. Advent Tower. Intel i7-3770 3.9 GHz 8-core. 8 GB System RAM. AMD Radeon HD 7700 1GB RAM. DVD ROM. 2 Terra Byte SATA Hard Drive. Philips 17" LCD Monitor. Saitek Cyborg X Fly-5 Joystick. ...and a Briggs and Stratton Petrol Lawn Mower.