Here's what E-flite says:

Option 2:
Motor: Power 46
ESC: Castle Creations Phoenix 60 (Standard settings with 12V Soft Li-Po cutoff and no brake)
Prop: APC 13x8E
Battery: Thunder Power PRO LITE 4200mAh 4S2P (THP42002S2PPL x2 in series)
Flying Weight w/Battery: 5.4 lb

Amps Volts Watts Input Watts/Pound RPM
47.4 14.1 670 124 8220

Expect strong performance with very short takeoff rolls and a great balance of thrust and top speed. Average duration is approximately 8 to 15 minutes depending on throttle management.

I usually get about 5-8 minutes on my 4S setup with this motor depending on how I fly. Maybe the motor overheated? Do you have enough cooling around the motor and ESC?