Got about 200' of this for 20 bucks. A friend had it in his shop and never used it due to the weight and length.

Running from an engine drive to a 211, how long would I be able to make an extension cord? I have seen post about this but not finding out enough.

Here in the manual for the 211, page 22

 When calculating max. cord length, remember to include conductor length from line disconnect device to input power receptacle.
Input Voltage
Input Power
Phase Hertz Conductor Size Max. Cord Length
120 V 1 60 14 AWG 27 ft (8 m)
230 V 1 60 14 AWG 53 ft (16 m)

http://www.millerwelds.com/om/o239988j_mil.pdf

And that's 14 gage that you can run 230v twice as far as a 120v?

Anyway, What would be the max length with 12/3 SO from the engine drive 230V receptacle? if possible?

I have made a few extension cords but always thought 12/3 was too small so I figured I would ask if this can be used with 230 for the 211.