If I remember correctly the clutch basket drives the oil pump which in turn drives the water pump via a small chain. So if all is correct you should not be able to spin the water pump shaft with out spinning the entire engine. In normal operation the water pump, oil pump and clutch are all connected to the crankshaft, so if you can spin the water pump driveshaft by it's self then something is not connected. The water pump drive shaft is just below the clutch assembly.