If you have an Aluminum impeller, there is a possibility it could bend. From my understanding, the impeller and shaft should be balanced for the best results. There shouldn't be much play in the shaft and should spin with nothing catching. I know Hardine Marine has all the parts for your JC-A pump. It is the same pump I have on my 1972 Tahiti. Also check out some YouTube videos on rebuilding the unit, you might find some useful info there as well.