The Yanmar 3GM30(f) on my Hunter 356 had its 1000-hour overhaul about 150 engine hours ago. It now experiences an occasional loss of power -- very occasional, three times in the last 100 hours. The engine rpms drop to about idle speed. If I close the throttle to idle, I can then speed it up to normal cruising speed, and it runs well for hours. I have checked the secondary fuel filter, thinking that there might be sediment in the bowl that gets stirred up and clogs the filter at at cruising speed, but I found it to be clean, with no sediment in the bowl. I have not checked anything else. Hs anyone had this experience and found the cause and a solution for it?