Hi: I have a 2000 Hunter 450 with the large Yanmar. Last month I met a fellow sailor who stated that you should never run a Yanmar below 2800. I think he said it had something to do with the exhaust elbow. I have not be able to find anything about this anywhere else. Has anyone else heard of this. The milage at 2800 is about 75% of that at 2500. Thanks
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80% of Maximum Cruise RPM..
..is what the Yanmar distributor recommended. Also that you do a few minutes of WOT after low RPM use, like charging batteries, etc. I think the manual will have the recommendation within it. Yes, from experience, the exhaust elbow will coke. I'm not sure that (if 3400 RPM X 80% = 2750 RPM) 250 RPM makes a huge difference. Your boat; dealer's choice. Good luck, RD
..is what the Yanmar distributor recommended. Also that you do a few minutes of WOT after low RPM use, like charging batteries, etc. I think the manual will have the recommendation within it. Yes, from experience, the exhaust elbow will coke. I'm not sure that (if 3400 RPM X 80% = 2750 RPM) 250 RPM makes a huge difference. Your boat; dealer's choice. Good luck, RD
I cruise at 3000
I've got the same 76 hp Yanmar that you do. WOT gives me almost 3700 rpm. 80% of that is close enough to 3000 for me. The Yanmars like to be run at higher RPM. Every once in a while I run it WOT for 10 or 15 minutes.
I've got the same 76 hp Yanmar that you do. WOT gives me almost 3700 rpm. 80% of that is close enough to 3000 for me. The Yanmars like to be run at higher RPM. Every once in a while I run it WOT for 10 or 15 minutes.
4JH2E
My yanmar mechanic advised taking it up to 3400 RPMs for a while every day to help clear the exhaust elbow. I generally cruise at 2800 turns, which is a couple hundred lower than what he recommended. Fuel efficiency aside, the engine has the best "feel" at 2800. My chief engineer, a tabby named Scupper, will only sleep on the engine cowling when I'm doing 2800. Anything slower than that and he's up in the cockpit, scrounging for crumbs; anything faster and he's hiding in his secret space under the oven.
My yanmar mechanic advised taking it up to 3400 RPMs for a while every day to help clear the exhaust elbow. I generally cruise at 2800 turns, which is a couple hundred lower than what he recommended. Fuel efficiency aside, the engine has the best "feel" at 2800. My chief engineer, a tabby named Scupper, will only sleep on the engine cowling when I'm doing 2800. Anything slower than that and he's up in the cockpit, scrounging for crumbs; anything faster and he's hiding in his secret space under the oven.
The story is true
The problem with diesel engines on a sailboat is that they are used for relatively short periods of time...once the sail is up they are shut off, or at low RPMs, like sharging the battery. Since the exhaust system never really warms up, the elbow will, over time, get carboned up, as well as excess carbon and glazing in the engine. To address this issue, you need to drive the engine harder than usual. In your owner's manual, max RPM of the 76 hp turbo is 3600, 90% of that is 3200, which would be the max extended cruising speed. 80% would be 2900, so an engine speed between these 2 would be ideal. Also, as mentioned in other posts, running at 3600 for 10-15 minutes occasionally is also recommended. A couple of other things to note: Always check the oil, particularly before your WOT run The turbo diesel MUST be warmed up prior to higher RPM operation. You can hear the turbo "whine" as it kicks in, if you hear this while the engine is cold, slow down The turbo diesel MUST be cooled off prior to shut down, particularly after a "burn out" run. Allow it to idle at the dock for a bit. The high speed run may produce smoke as the crud burns out. If this happens, slow down to cruising speed. Also, I am not a mechanic. This information came from the Yanmar booth at a boat show, and seems to agree with what others have told me.
The problem with diesel engines on a sailboat is that they are used for relatively short periods of time...once the sail is up they are shut off, or at low RPMs, like sharging the battery. Since the exhaust system never really warms up, the elbow will, over time, get carboned up, as well as excess carbon and glazing in the engine. To address this issue, you need to drive the engine harder than usual. In your owner's manual, max RPM of the 76 hp turbo is 3600, 90% of that is 3200, which would be the max extended cruising speed. 80% would be 2900, so an engine speed between these 2 would be ideal. Also, as mentioned in other posts, running at 3600 for 10-15 minutes occasionally is also recommended. A couple of other things to note: Always check the oil, particularly before your WOT run The turbo diesel MUST be warmed up prior to higher RPM operation. You can hear the turbo "whine" as it kicks in, if you hear this while the engine is cold, slow down The turbo diesel MUST be cooled off prior to shut down, particularly after a "burn out" run. Allow it to idle at the dock for a bit. The high speed run may produce smoke as the crud burns out. If this happens, slow down to cruising speed. Also, I am not a mechanic. This information came from the Yanmar booth at a boat show, and seems to agree with what others have told me.
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