What HK says about max. watts is typically BS. That 2836 should be capable of dealing with a bit more power than the smaller 2826 (~150W) or 2830 (~180W) motors... but 338W is waay over the top for a 70g motor - the 3W/g rule of thumb suggests 210W max.
I can't speak for the stock motor but a Suppo A2212/13 (~1080Kv) [roughly the same weight and Kv as the 2826/2830 motors you linked to] with a 9x5 GWS HD drew 10.45A/113W.. pitch speed was ~40mph.
The Suppo A2217K/9 (70g, ~1035Kv) [matching the weight and Kv of your Turnigy 2836], with that same 9x5 GWS HD drew 11.95A/130W with 42.6mph pitch speed.
If you cannot go to 4s, then you need higher Kv and a higher pitched prop to get sufficient speed and power from 3s, to improve your Mustang.
For example, if you used a 70g Suppo A2217K/6 (~1530Kv) on 3s with a 7x7 APC Sport prop you would get 21.20A/227W and 27oz thrust @ 87mph!
Last edited by Dr Kiwi; 08-31-2013 at 07:20 PM.