Any folks know 220 wiring ?

Thanks...time to catch up.

No room in the breaker box..maxed out. Would prefer not to use the dryer plug because it messes with the mom..

It is a portable generator. It is a 4000 watt 7.5 hp machine with a 120/240 20 amp plug. The compressor is a 2 hp craftman 240 that has the old style 3 prong plug. the wires are hot black / white with green ground.

I have a 20 amp. 125/ 250 volt 3-Pole 4-Wire Grounding plug that I am trying to wire up with the 3 wires. On the back of the plug I have a green and three brass screws. However, if I spin the plug around as in the picture above and put the ground TDC, the prong directly below is silver so I am assuming that this is neutral. I am borrowing a curcuit tester tomorrow to verify which is which.

Before I was thinking, I did wire up the plug with what I thought were hot and ground and the compressor didn't seem happy since I thought the 4th plug, neutral I gather, wasn't necessary.

I looked for extra specs on the compressor but it is an old one..early 80s I think.

Wouldn't hard wiring it be the same think that I did ? Would it matter which hot I put the black/white to ?

Is my gen large enough ?

Thanks
Grassy