Yes, the shaft should freely turn. If it doesn't, it's probably the bearings that got wet last year when your impeller snapped off. Did you change the shaft seal assembly when you replaced the impeller?

If not, I'll 'double down' on my guess that the bearings need to be repacked. (for everyone's edification: when you change out an impeller, it's best to replace the shaft seal assembly as well- it's another $10- 20 but, the seals are prone to failure once removed and can/ will leak, which puts the bearings and other motor components in jeopardy of failing or seizing up).

I hope Al will clarify things for me ( I don't always express myself properly on the 'nuts and bolts/ physics' part of repairing things)