My 1986 Yanmar 3GM 30 with approx 2k hours revs up to around 34K RPM's when not in gear, but only around 2100 in gear. She starts fine and runs smooth. She does not run hot. I have changed the fuel filters (both for inlines, but not the screen in tank). There also is grey exhaust smoke that I have not noticed before. I have cleaned the prop, but there was very little growth on it. It did not make any difference. I have been told that it could be an exhaust problem, but I don't understand why it could rev up when out of gear, and not rev up in gear if it were an exhaust problem. The shaft turns easily by hand, and does not seem to bind. I have noticed that my packing gland does not appear to leak its required on or two drops under way, but it does not smoke or get hot. Could it be binding anyway in spite of the fact that the shaft turns ok by hand?
This is a recent problems as she was running fine in the spring.
So to summarize, does the fact that the engine revs up well out of gear but not in gear help eliminate some of the possibilities with exhaust issues or fuel line issues? I don't find this particular scenario addressed in "Trouble Shooting Marine Diesels".
Thanks
Keith
P.S. I had posed this question in the body of an earlier thread, but since it got no replies, i thought I would repost as a new thread.
This is a recent problems as she was running fine in the spring.
So to summarize, does the fact that the engine revs up well out of gear but not in gear help eliminate some of the possibilities with exhaust issues or fuel line issues? I don't find this particular scenario addressed in "Trouble Shooting Marine Diesels".
Thanks
Keith
P.S. I had posed this question in the body of an earlier thread, but since it got no replies, i thought I would repost as a new thread.