2QM15 specifications
The Yanmar 2QM15 engine is rated at 3000 RPM, 15 HP for one hour, 14 HP continuous. Mine is a year older than yours, and I generally run it at 2050 to 2500 RPM. For years I automatically ran it at 2350 RPM, always. Now, since I have more loads on the engine (bigger alternator and more junk, which makes the boat tougher to push), I tend to back off a bit. I still don't hesitate to run the engine at 2400, and will occasionally push it up to 2600, but also spend more time in the 2050-2250 range than before. Yanmar recommends an hour at FULL power, every thirty or forty hours or so, to blow out any carbon and minimize glazing of the cylinder walls. My problem is that I have enough stuff on the stern of the boat (windvane, outboard, solar panels, etc.) so that she squats just a bit, when powering at over 6 knots. The little "tail" at the bottom of the transom submerges, up goes the drag, and the engine REALLY has to push, to the extent of smoking a bit. So, I tend not to do this. I used to be able to achieve the rated RPM (3000), while underway, (which you SHOULD be able to do), but, for the reasons mentioned above, I can't quite get there. Last year, I took an inch out of the pitch of the prop with NO negative consequence on the speed, and a little easier load on the engine at high RPM. In retrospect, I would like to have taken two inches out, since I believe I might have gotten the RPM back up to almost 3000. As it is, my maximum is about 2850 RPM. In general, this is an extremely reliable engine, if properly cared for. Make sure to change your zincs. As Steve Dion mentioned, change oil and oil filters regularly. Of course, the snag is that this job is a bitch. I recently took the oil pan off, and drilled and tapped a drain, to which is fitted a valve and then a hose and bulb pump such as you see on an outboard motor fuel line. With that, I can now evacuate ALL the oil in about thirty seconds, no muss no fuss. I am still kicking myself for not having done this years ago. My next little addition will be to add a remote mount for the oil filter, which will be vertical rather than the horizontal position on the engine. Then, I will simply be able to drop the oil filter off like you can do in a car, without spilling oil all over the place. At that point, I will be able to do the entire job of changing oil and filter in about five spill-free minutes, and will, no doubt, be cursing the fact that I waited twenty years for THIS modification. Needless to say, I have no intention of getting rid of this engine. She still starts quickly and runs very well. I suppose a rebuild will be in order in the not too distant future, and all the parts are still available. Since I am in the final countdown to a major cruise, I will probably take all the spares with me, and eventually do a rebuild in some exotic place! Good luck with your engine.
