Seawater pump question/impeller

If you take the serpentine belt off should the seawater pump pulley spin with little effort?
I have a feeling it took a sh#t on me today. All of the other pulleys except the crank pulley turn with little effort. Idler pulleys alt. etc.
When I turn the seawater pump pulley it's hard to even turn a little bit. I'm guessing impeller took a doo doo but I dont have a mercruiser manual yet so any help would be apreciated.

They only turn easy when all the blades are wet and going the same direction. If you moved it back and forth you probably have some of the blades facing one direction and some facing the other direction. It is also quite possible that a couple blades broke off and they are jamming things up. If the impeller is over a year old just replace it.