Wire AC Condensor fan motor to three prong plug for shop fan
Mains wiring is dangerous

You're not allowed to just barf a bunch of wires and call it done.  The fan, I assume you scrounged this from an old air conditioner, is made to fit inside a housing, which you have removed.  You need to head off to the metal press to restore two key functions of the housing: Physical protection from fan blades, and electrical protection for the wiring.  

Once that is done, you can fit an appropriate cord and strain relief onto that housing.

The fan is almost certainly 240V

... Since most air conditioning units hook up 240V no neutral. The motor will not like 120V because it's simply the wrong voltage.  There's nothing you can do with the start capacitor to improve that.  

Which means it can't be powered from 120V (unless you do some very graduate-level stuff that's way out of your depth and would be prohibitive in cost, since I assume the point here is to scrounge/be cheap).  It needs to be powered from 240V, which means it needs a different type of plug. 

You need a NEMA 6-15 (I presume this isn't a 3600 watt fan).  This has the 2 blades rotated 90 degrees, so they are flat to each other.  See #3 here



This in turn means you'll need to run a 240V circuit to your garage if you don't have one already.  However they are rather useful, and let you get good deals on 240V tools on Craigslist from people who didn't know what they were buying and are now stuck with a white elephant. 

The temptation for the novice cheapie is to hork this up in some non-code-compliant way.  That's just dumb.  Cheap is not the same as stupid.  Aside from potentially killing you in the interim, the inspector will require you put it right when you sell the house, and that usually turns into an  expensive fiasco because you're in a hurry to close.  There are some things you don't mess with, and electrical is one of them.