That’s a pretty common motor used on a lot of compressors normally they call it a 5HP 56 Frame. I think they can be had new for around $200, and I know it would be nice to know it is the problem before spending that amount. To replace the whole thing with a 2 stage might be $1500.The motor is: 3.1 RHP, 7 Peak HP, 3450 RPM, 56 Frame, 208/220 Volts, Single Phase, 5/8" Shaft
The compressor is a single stage, belt drive Sanborn 60 gal compressor.
The compressor is about 16 years old and gets regular light usage, e.g., 1/2 to 1 hour of usage per month.
I would see if you have a local shop to look at it.
Good luck.