I have a 100 Yamaha four-stroke that has run like a top since I bought it almost 3 years ago. Yesterday, heading out at full throttle, the engine lost power and the buzzers came on. Water was pumping fine and in fact the pump has been replaced within the last 3 months. Upon restart after checking everything, I could hear a distinct knocking sound and the engine definitely put out more smoke than usual.. Got a tow in. Any thoughts as to the problem? Thanks! David-Beaufort, NC