undergeared?

[RUSTY XL-5]

Well, I have a rusty with flightmax 3s 30c 5000mah lipos and a medusa 4800 kv. Gearing is 17/83 but the esc gets to 180ish in 20 minutes or so and I have to let it cool to prevent thermaling...motor consistently runs 150. I heard if batts are cool (they are always under 80), motor cool, and esc hot your under geared. Is this correct? Would a 19t pinion be a better choice or should I solder on a cap?


Thanks.