"Oil Pressure Alarm not functional" Although we haven't heard from Peter for some time, my take is that the engine oil pump is not working 'fully' or one of the oil passages is clogged. Although in a completely different machine, a motorcycle, I had the same symptoms happen to me. I tore down and rebuilt the engine, but I left a metal shaving in it...it got stuck in one of the oil passages. I'd have full power for a few minutes, then a progressively louder tap to knocking sound, and power would fall off, until all I could do was idle. With an engine with a water jacket, it would probably keep temps from going out of control. A IR thermometer would likely find the hot spot and the place to look...