"but I dont know enough about balancing motors and props for economy and performance."
Think of it this way..the prop is the final gear in the whole scheme of things.The best you can hope for is a prop that will drive the errr allow the engine to reach the mgf's maxium rpm band ...4800 is a safe bet.
The rest your just stuck with...speed....mpg....and performance characteristics...Now you can fiddle with your carb timing and cams whatever plz's you but its like a car with 1 gear from start to stop..not much to tinker with there.
3 blade props offer the highest speed
4 blades offer the best midrange
There are some differences in econ between the two....But really very little practical difference
http://dictionary.reference.com/browse/a-yuh
a-yuh
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ˈeɪ
yə, eɪˈyʌ/
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ey-y
uh, ey-
yuh]
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?interjection New England . (used to express agreement); yes
Here let me get you up to speed:
http://www.google.com/#sclient=psy&...=&aql=&oq=&gs_rfai=&pbx=1&fp=207a1c3c62b92b94

Pay some attention to that a-yuh...