Hmmm looks like you got the same motor, i have, just with different "T's"
Sounds like a 10T one
Slash on 5S ? Thats a lot power. how much mA do your batteries have ?
I have 3S 6500mA and get almost 25min runtime Indoor so around 73Wh
A 4000mAh on 5S would be around the same (74Wh)