HELP! I have an Electric Phoenix trainer and am having trouble with correct prop and battery selection.

Current Setup:
e-flite 32 motor (700w)
60A speed control
10x6E APC prop
3 cell LiPo 3300 battery.

This gived me around 6 minutes of flight time.
I was flying yesterday and I was advised by fellow modellers that the prop was too small for that size motor.
If I increase the prop, won't I get less flight time?
What about if I go to a 4 cell pack?

It depends - a larger prop will draw more current at wide open position, but a larger prop also tends to be more effeicient, so provided you show some restraint you may get more thrust for your watts with a larger prop.

If you go to a 4 cell pack the motor will spin faster, drawing more amps. You will be able to go faster but you may need a smaller prop to stop the motor getting overloaded.

Thing to do is to get yourself a wattsup or other power meter and actually measure your current flow with different props - that way you can pick the right prop that doesn't overload the battery/ESC/motor etc.

Cheers,
Oz.