Increasing engine power

I downloaded a HP42 aircraft, which is a very old dinosaur and is very very slow.  I have no problems with the aircraft, it flys well and everything seems to work, however the airspeed leaves much to be desired.  The specs indicate that it's max speed could be 181KIAS, which would be incredibly fast however it should be able to cruise at around 100 to 130 KIAS.  Ha Ha  no way.  I am lucky if I can get to a little over 70 KIAS.  I took a flight from Gatwick to Isle of Man and my average KIAS was 75.  Is there a safe way to boos the engine power?  I have looked in the engine section of the airfile and am a little reluctant to mess with the settings.  I guess I could simply try a trial and error approach, but I am hoping someone out there knows something about adjusting engines.   Thanks.