Edmond,
This is becoming a pretty common question. There are a lot of folks using corded blowers to run their smaller dry washers. I do suggest that you buy a unit of at least 300cfm preferably a 400cfm. If all you are going to use it for is as a blower for a Drywasher then I would also suggest a unit that is rheostat controlled to adjust your air flow or install a simple dampener in the hard tube. this will allow you to precisely control the air flow and will help in recover. Just think of them as throttles on a gas blower.

Good luck and get out there finding gold.

 Kevin