How to keep my old school Mamba Max from overheating on 3s.

[simplechamp]

Capacitors on the power input of the ESC. The ESC has a few built-in, but many people add extra. Castle makes a cap bank, or you can buy caps and make a bank yourself. You need low ESR caps, and make sure to leave overhead on the voltage rating (get higher voltage rating than you plan to use, it's harder on the caps if they are running at their max rated voltage)