The fan on my Tempstar outside unit slows after about 45 minutes of running, then comes to a complete stop. There is a smell as if something is hot. I have replaced the fan motor, capacitor and contactor with no change. Where do I go from here?

Call for professional service.OR you can keep replacing parts and spend more money.

You could have the wrong HP fan/wrong fan blade/wrong fan motor capacitor value.
Your coil could be so dirty that the fan becomes overloaded after awhile and causes it to shut off.

The fan motor depends upon the air moving through the coil to keep it cool. No air movement due to dirty coil can cause motor overheat.