I just purchased the Hunter 41 ds with a Yanmar 56 horse, what is a good rpm to keep the motor from working to hard but maximizing best constant power. At 3000 rpm it goes about 8 knots. Is 3000 rpms too high to run the boat at a study pace? Thanks
Yanmar 56 horse
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normally 70-80-% of max rated RPM
Christian: Most of the Yanmars should be run at 70-80% of the max rated RPM. If you engine is rated at 3600 rpm (max), this would be 2500-2900 rpms.
Christian: Most of the Yanmars should be run at 70-80% of the max rated RPM. If you engine is rated at 3600 rpm (max), this would be 2500-2900 rpms.
and keep in mind that your boat tach in the boat..
may read 200 too high so 3000 may actually be 2850 +/- abe
may read 200 too high so 3000 may actually be 2850 +/- abe
Manual
I have a 56 hp also and I ask Yanmar how to operate it and on occasion its ok to run it @ 3600 for a short time (5 min)to blow out the carbon build up. If you don't run it for hours @ 2800 you should run it @ 3000 for short runs (20 min to 30 min). Its a good pratice to go for a long run every now and then just to keep your engin carbon free (also a good excuse if needed) the manual has some of this info in it. good luck
I have a 56 hp also and I ask Yanmar how to operate it and on occasion its ok to run it @ 3600 for a short time (5 min)to blow out the carbon build up. If you don't run it for hours @ 2800 you should run it @ 3000 for short runs (20 min to 30 min). Its a good pratice to go for a long run every now and then just to keep your engin carbon free (also a good excuse if needed) the manual has some of this info in it. good luck
3,000 too high IMO
We also have the 56 in a 41 AC model, 2005. The manual that came with this engine has guidelines on how to run it at what rpms. I don't have the manual with me right now, but you need to look at it as your best guide. I believe 3,000 is too high rpm for extended normal running. This engine runs max rpm of 3,200. We usually cruise at 80% of that. Per the manual, you can go higher, but only 5% of the time if I recollect correctly. As Abe mentions, key to this is having an accurately calibrated tachometer. Ours was not calibrated correctly but a good mechanic can easily calibrate it for you. The tach reads off the alternator. We opted for the optional Balmar alternator (factory installed), but Hunter did not recalibrate the tach to match. We were off by about 200 rpm too high on the tach. If you can run WOT at 3,200, you are probably calibrated about right (assuming your prop allows it and you have a clean bottom etc). Happy motoring!
We also have the 56 in a 41 AC model, 2005. The manual that came with this engine has guidelines on how to run it at what rpms. I don't have the manual with me right now, but you need to look at it as your best guide. I believe 3,000 is too high rpm for extended normal running. This engine runs max rpm of 3,200. We usually cruise at 80% of that. Per the manual, you can go higher, but only 5% of the time if I recollect correctly. As Abe mentions, key to this is having an accurately calibrated tachometer. Ours was not calibrated correctly but a good mechanic can easily calibrate it for you. The tach reads off the alternator. We opted for the optional Balmar alternator (factory installed), but Hunter did not recalibrate the tach to match. We were off by about 200 rpm too high on the tach. If you can run WOT at 3,200, you are probably calibrated about right (assuming your prop allows it and you have a clean bottom etc). Happy motoring!
RPM recomendations
The 4JH3 engine you are refering to is a 3600RPM engine. This is the MAX 1 hour rating. Max continous rating should be 3400RPM. A cruise range would be 2800-3200RPM The tachs do have a history of reading 200RPM off and are easily adjusted. Yanmar tachs do not read from the alternator, they have a sensor that counts the flywheel teeth. Abe, in that 2005 you might have a 4JH4 engine which is rated diferently than the earlier 4JH3 Pat McCartin Inland Marine Diesel Buford, Ga imd_ga@hotmail.com
The 4JH3 engine you are refering to is a 3600RPM engine. This is the MAX 1 hour rating. Max continous rating should be 3400RPM. A cruise range would be 2800-3200RPM The tachs do have a history of reading 200RPM off and are easily adjusted. Yanmar tachs do not read from the alternator, they have a sensor that counts the flywheel teeth. Abe, in that 2005 you might have a 4JH4 engine which is rated diferently than the earlier 4JH3 Pat McCartin Inland Marine Diesel Buford, Ga imd_ga@hotmail.com
Engine model
Yes, we have the 4JH4E, not the 4JH3. Pat, thanks for the correction on how the tach reads. My mechanic attributed the tach discrepancy to the alternator swap and I believed him!
Yes, we have the 4JH4E, not the 4JH3. Pat, thanks for the correction on how the tach reads. My mechanic attributed the tach discrepancy to the alternator swap and I believed him!
Max vs Max continous
If the max 1 hour rating is 3600 and the max contious is 3400 as Pat said, you should be able to contiously run at 3400. Diesels like to be run hard as it prevents/reduces carbon build-up and cylinder glazing. Running at a crusing RPM might make sense if that gives you better fuel mileage but that is not the usual case for a diesel engine. Most are at max efficency at their max continous RPM. And of course you have to factor prop losses, wind, waves and current.
If the max 1 hour rating is 3600 and the max contious is 3400 as Pat said, you should be able to contiously run at 3400. Diesels like to be run hard as it prevents/reduces carbon build-up and cylinder glazing. Running at a crusing RPM might make sense if that gives you better fuel mileage but that is not the usual case for a diesel engine. Most are at max efficency at their max continous RPM. And of course you have to factor prop losses, wind, waves and current.
Operating guidelines
Christian, First, check the plate on top of the engine and get an accurate reading of the model number, including the max rpm rating. Then, check this site for their recommendation. http://www.yanmarhelp.com/operate.htm I have the 4JH3BE model with a maximum rating of 3600 rpms and 56 hp, and our Yanmar dealer strongly recommends to cruise at 3000 rpm. My particular engine has 883 hours in 5 years and runs like a Rolex watch and uses no oil. These engines need to be run so their internal temperature reaches a point to run efficiently. This is different than the coolant temperature. Also, at this engine speed, our boat averages about 1.1 gallons per hour fuel consumption. The worst she has ever gotten was 1.5 coming up the coast of Mexico, into current and a 5 foot swell. The proof is in the pudding as they say. John Richard s/v Jack's Place
Christian, First, check the plate on top of the engine and get an accurate reading of the model number, including the max rpm rating. Then, check this site for their recommendation. http://www.yanmarhelp.com/operate.htm I have the 4JH3BE model with a maximum rating of 3600 rpms and 56 hp, and our Yanmar dealer strongly recommends to cruise at 3000 rpm. My particular engine has 883 hours in 5 years and runs like a Rolex watch and uses no oil. These engines need to be run so their internal temperature reaches a point to run efficiently. This is different than the coolant temperature. Also, at this engine speed, our boat averages about 1.1 gallons per hour fuel consumption. The worst she has ever gotten was 1.5 coming up the coast of Mexico, into current and a 5 foot swell. The proof is in the pudding as they say. John Richard s/v Jack's Place
yanmar 56
This is my second season with the 41DS. I run my Yanmar at 2900 RPM when motoring. Good speed and fuel economy. I average about 7.5 kts @ 2900Rpm and burn about 3/4 gallon per hour. Do you have the dual fuel tanks on your new 41DS? If so, I will tell you separately the problem and learning curve I had with it.
This is my second season with the 41DS. I run my Yanmar at 2900 RPM when motoring. Good speed and fuel economy. I average about 7.5 kts @ 2900Rpm and burn about 3/4 gallon per hour. Do you have the dual fuel tanks on your new 41DS? If so, I will tell you separately the problem and learning curve I had with it.
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