Chris, does your motor have a capacitor on it ? The capacitor will be enclosed in a metal cap like thing about 3" long, 1 1/4 across the base and normally have a rounded top about 1-1/4" high. About big enough to put a 3" peice of a hot dog inside.

If it is a capacitor start motor, you should be working on a
"Plan B" because there is a good chance the motor will crap out, especially if you run it slow. To be assured of a reasonable life exepctancy you need a "shaded pole" motor. They do not have capacitors. The most common place to see these is in ceiling fans. That is the kind of motor Leader and others use for air under the fire systems.
If the sap guys will take it back, ship it and order a proper high pressure radial blower with shaded pole motor from Grainger or McMaster Carr. After all that work you won't want to go without your air system 6 hours after the season starts.