[sswee]

Your thinking about it in reverse. The size of the wheel doesn't matter to the RPM only to the SFPM. The 2 hp motor will still only turn 1750 RPM's with a 8" wheel but you would slow your SFPM down and go the opposite way you are wanting.

A 8" wheel at 3450 RPM turns 5131 SFPM
A 10" wheel at 1750 RPM turns 4581 SFPM
A 12" wheel at 1750 RPM turns 5497 SFPM

If you go to the slower 2 hp motor with a 12" wheel, you would be getting more surface feet per minute and more the direction you want to go.

Hope this helps.
SS