I use a bilge pump on my boat to pump water into my live well. I been havig problems with it lately. Sometimes when I turn it on it comes on but doesn't pump water but while it is on I will unclamp the hose from the outflow connection and it will pump water. I will then reconnect the hose while the pump is on and it will work fine for a while then it will just quit pumping water but the motor is still on. Any thoughts or suggestions? It will work fine at times without doing anything to it.