How deep are you running the skimmer? Depending on the depth, it may answer the overflow question. In terms of the chatter noise, it may be the impeller that has gone bad. The pump is out of warranty so you can either purchase an impeller to try to fix the issue or purchase a new pump instead. It is hard to know what the issue is unless our techs can inspect the pump. You can send the pump in for repair but at that point, you will be better off just purchasing a new pump.