speed control getting hot.

[hotbodies racer]

well i have a lcc with a 9100t servo, cc bec set at 6.0v, a titan 21 turn motor 10t pinion, a fan on the motor, with a 16.8v e-maxx speed control. with a 4-cell and a 4-cell cut off. if i run it for a while the esc get's hot 150 or so. only noticed when going slow, i was trying to see how steep i can climb. the last time it got warm was when i didnt have a bec, so i hooked it up, and yes the red wire is unhooked. i dont know what's left to do. i've tryed runing without the cut off but thats not it. i know i cant run it without the bec. so what do you guy's think. im running out of options the only thing i havent done is change the motor, it's kinda old.