Yoav,</p>
it is not just about the maximum power, because let's not forget that a Ferrari has 500HP and a big truck can have the same power too, but they are 2 completely different things.</p>
But not to complicate the life too much with explanations right now let's stick to your combo. First of all if you want to push that motor to 500-550W you would need to change your ESC to 60A because, usually, a 3S bat under load gives some 10-10.5V, therefore for 550W you need 55A. As your current ESC is only 45A that would not be enough, and lets not forget that ESC is also supplying your servos and receiver with power, so has additional load.</p>
As I have a motor with same kV 900 I have played a lot with different props so I think I can give you some good advice
.</p>
In general for F3A type of flying you need a prop that gives you good reserve of power, and this you get from higher pitch. You don't need to go much in static thrust above 1,5:1 (thrust:weight) but you want to have is as much reserve of power as possible from your cruising speed in horizontal line to be able to maintain speed in verticals. So a 13x8 or 13x10 is what you need here. Don't forget that different brands of props can give (very) different results, so my vote goes to Turnigy light electric. I think that with 13x8 you can even keep your current ESC, usually 40mm motors are more efficient than 35mm, the one I have.</p>
At the same time 3D type of flying needs something completely opposite. A lot of static thrust and low max speed. Hence a 14x7, 15x8 would be great to give you up to 2:1 ratio, which is what you need for 3D.</p>
The beauty of electric is that one same motor can successfully be used on many completely different application from F3A, 3D to warmliner.</p>
And last but not least. The static measurement taken on the ground is just an indication of how good is your combo. Prop unloads a lot in the air and my guess is that with your current combo you had very good flying time but the throttle stick was at 2/3 at least all the time and the reserve of power was very low. I believe it is now more clear why.</p>
Velco</p>