No it's not crazy. Many spa/pool motors are 2 speed (slow speed is usually much less power). It may have a weird shaft. Many are NOT reversible. My Dad had an old pool pump motor on a drill press for years. It is 0.75 hp on high (1725rpm) and 0.21 hp on low(1140rpm) . It worked fine, I still have it and I'm planning to use it on my Atlas mill. If it were me I would give it a try!
For a number of years, I worked on spas. It seems to me that spa motors should work on a lathe. Most that I know of are capacitor start. Many are two speed, low speed for circulation and high for jets. If single speed then it was high speed in order to run the jets. A small motor would run the circulation. Now a couple things to watch for, there were a lot of cheap spas that used really low grade motors( we had to replace one where the shaft actually broke). The other thing is check the bearings. If you see what looks like a white powder coating the motor especially where the pump was fastened, it is calcium. That calcium comes from the owners neglect. The calcium is like sand and gets in the bearings and ruins them. I made lots of money from replacing motors or getting them repaired, because the owners would not do some simple maintenance. Good luck and let us know how it works out. Mark
It probably has a tapered shaft to mount the impeller. I built the end up with weld and turned it down, then cut a keyway to use it on a pressure pump. Works well but seams low on startup torque, won't start the pump against the unloader valve, have to hold the handle open on the first start, then its fine.