Posting on behalf of a friend - subject boat is a Jeanneau 36.2 with a Yanmar 3GM, less than 900 hours. The engine starts well, and will run to WOT (3600 rpm) in neutral and in reverse. In forward however it will only develop around 3000 rpms, with lots of black smoke. The boat reaches hull speed moving forward (7+kts) at relatively low rpm - less than 2500. The prop is a Radice OTK11R, stamped 16 10 which is the original factory spec. To date the items undertaken to solve the problem include inspection of exhaust elbow, which was determined to be clear, compression test (410 420 410), valve adjustment to factory spec, injector rebuild to spec. The bottom and prop are very clean. Any thoughts or suggestions?