i own a 84 H31 with a Yanmar 2gmf. i can only get 2500 rpms in neutral. is this normal ? if not, what could be the cause. PS: can anyone tell me how to check the engine alignment?
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Too low don't you know
Bob: My Yanmar rep in Richmond, CA. claims that the engine should be able to rev to 3600-4100 in netural. I have a similar problem but have eliminated the primary cause of this which is the mixing elbow. They get coked up from running the engine at low RPM's. The elbox is on the back of the engine attached to the head. The exhaust hose attaches to the elbow and the fresh water intake mixes with the exhaust in this unit. I would recommend that you purchase a new elbow and gasket and replace yours (about $100) but no labor because you can do this yourself. I will tell you that getting the elbow off of the exhaust hose and manifold is not an easy chore. Make sure that you have something like WD40 to help remove the hose. I used a screw driver to loosen the hose and then squirted the WD in the hose and then it came off easily. Once the elbow is loose from the hose you can remove the exhaust manifold. There are four bolts that hold it to the head. These where easy to remove on my boat even after 13 years. The next step is the biggest problem and it involves getting the elbow off of the manifold. Once the manifold is off the engine you will probably need a LARGE vice to remove the elbow. I believe that it has a reverse thread. We finally got ours off with the use of torch by heating the elbow (cast iron). When you put the new elbow on be sure to coat the threads with nosize. The final step is trying to get this back on the engine. I used some tape on the gasket to hold it in place but I think that some of this gasket stuff will hold it in place making it much easier to replace. Once you get two bolts started you are pretty much home free. BE SURE TO TIGHTEN ALL of the hoses before you start your engine. If you do not want to buy a new elbow you can TRY to clean up the old one. I understand that acid will clean them up? (not too sure about this one) If this does not fix the problem then you need to have a Yanmar mechanic look at your governor. This is an easy thing for them but not recommended for an amature. You engine should be able to rev to 3600 at WOT (wide open throttle) when under way. You should NOT run your engine for prolonged periods of time under 70% of max ratings. The normal operating range for these engines is 2500 - 2900. You can run the engine up to 3400 for up to 1 hour if needed. This is assuming that you have the correct prop. Your engine should rev to at least 3600 when under way if everything is correct. If you cannot get these RPM's underway your prop is probably overpitched (which I think is the case based on what I hear from other H'31 owners) I am now testing a composite prop from CDI. I will know if it is working properly once I get my govenor adjusted. Good luck, I hope this helps.
Bob: My Yanmar rep in Richmond, CA. claims that the engine should be able to rev to 3600-4100 in netural. I have a similar problem but have eliminated the primary cause of this which is the mixing elbow. They get coked up from running the engine at low RPM's. The elbox is on the back of the engine attached to the head. The exhaust hose attaches to the elbow and the fresh water intake mixes with the exhaust in this unit. I would recommend that you purchase a new elbow and gasket and replace yours (about $100) but no labor because you can do this yourself. I will tell you that getting the elbow off of the exhaust hose and manifold is not an easy chore. Make sure that you have something like WD40 to help remove the hose. I used a screw driver to loosen the hose and then squirted the WD in the hose and then it came off easily. Once the elbow is loose from the hose you can remove the exhaust manifold. There are four bolts that hold it to the head. These where easy to remove on my boat even after 13 years. The next step is the biggest problem and it involves getting the elbow off of the manifold. Once the manifold is off the engine you will probably need a LARGE vice to remove the elbow. I believe that it has a reverse thread. We finally got ours off with the use of torch by heating the elbow (cast iron). When you put the new elbow on be sure to coat the threads with nosize. The final step is trying to get this back on the engine. I used some tape on the gasket to hold it in place but I think that some of this gasket stuff will hold it in place making it much easier to replace. Once you get two bolts started you are pretty much home free. BE SURE TO TIGHTEN ALL of the hoses before you start your engine. If you do not want to buy a new elbow you can TRY to clean up the old one. I understand that acid will clean them up? (not too sure about this one) If this does not fix the problem then you need to have a Yanmar mechanic look at your governor. This is an easy thing for them but not recommended for an amature. You engine should be able to rev to 3600 at WOT (wide open throttle) when under way. You should NOT run your engine for prolonged periods of time under 70% of max ratings. The normal operating range for these engines is 2500 - 2900. You can run the engine up to 3400 for up to 1 hour if needed. This is assuming that you have the correct prop. Your engine should rev to at least 3600 when under way if everything is correct. If you cannot get these RPM's underway your prop is probably overpitched (which I think is the case based on what I hear from other H'31 owners) I am now testing a composite prop from CDI. I will know if it is working properly once I get my govenor adjusted. Good luck, I hope this helps.
same/same
'Nother viewpoint: -I cleaned out the mixing elbow this season; under 10 minutes and no particular hard work. I used an old toothbrush and some soap. I didn't notice a gasket (last owner removed it?) but it doesn't leak. Incidentally, if its rusted, replace it immediately. -Bought a CDI 3 blade composite this season. Luv it. Incredible in reverse; I guess it adds 1/3 - 1/2 knot forward under sail; powers OK. Between this and a newly stripped bottom, I've been embarrassing some much "faster" sailboats lately. Some reasons for low RPM: -Not enough air. Does it change with the engine uncovered (too tight engine box - cut a hole)? What does your air filter look like (clogged - wash it)? -Not enough fuel. Try moving the throttle **directly at the engine** and see if the RPMs increase (throttle cable binding - replace it.). Does the exhaust go black? (i.e. if not, maybe not enough fuel - is fuel filter OK? is fuel separator OK?). -Governor is mis-set (get a manual or hire a mechanic). -Karma is bad. (Sacrifice a chicken over the valve cover. I like Purdue Oven Roasters.)
'Nother viewpoint: -I cleaned out the mixing elbow this season; under 10 minutes and no particular hard work. I used an old toothbrush and some soap. I didn't notice a gasket (last owner removed it?) but it doesn't leak. Incidentally, if its rusted, replace it immediately. -Bought a CDI 3 blade composite this season. Luv it. Incredible in reverse; I guess it adds 1/3 - 1/2 knot forward under sail; powers OK. Between this and a newly stripped bottom, I've been embarrassing some much "faster" sailboats lately. Some reasons for low RPM: -Not enough air. Does it change with the engine uncovered (too tight engine box - cut a hole)? What does your air filter look like (clogged - wash it)? -Not enough fuel. Try moving the throttle **directly at the engine** and see if the RPMs increase (throttle cable binding - replace it.). Does the exhaust go black? (i.e. if not, maybe not enough fuel - is fuel filter OK? is fuel separator OK?). -Governor is mis-set (get a manual or hire a mechanic). -Karma is bad. (Sacrifice a chicken over the valve cover. I like Purdue Oven Roasters.)
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