Quincey Compressors are of high quality. I think your motor may be newer than the compressor/tank. Replacing the start capacitor would be a good next step on a project like yours.
Paul, I agree with your suggestion. The motor is newer for sure. It looks like it has 3 capacitors (or is one of the small 3 top motor housings not for a capacitor), is the best way to identify the start capacitor to look at all 3, with the highest microfarads being the start capacitor?
Once again, I'm out of my comfort zone.
edit; once again more searches yield more info. Seems the middle housing on top isn't a capacitor. To answer my own question, I removed the covers and the start capacitor is pretty easy to identify, it's the one that's about 50% bigger.
RonR