I have a 30 HP Yanmar turning a two blade prop. When the throttle is pushed all the way forward, the Tach reads 2000 RPM's at its highest RPM. Is that what it in fact should be reading? I am not blowing black smoke and there are no overheating issues. I just wondered if that was what the proper RPM should be showing in calm water, little or no current with the little red handle against the guard (as my wife would say). ALSO.......I still am trying to decipher if my 81 model should have a 16 x 14 RH folding Prop...if my wife finally decides to let me have one. Thanks for responding.... Frank Bean S/V Blue Shark Mobile, Alabama
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depends on the model of the engine, but.....
Frank: Depending on which Yanmar you have there is a slight difference in the max RPM's. Most of the engine were rated at 3600 rpms max. They should be cruised at 70-80% of the max rating (normally 2500-3000 rpm). There are different things that could be wrong, starting with the tach. You may want to have a Yanmar repairman take a look at your engine. As far a prop's are concerned I would be sure that you get the advice of the prop shop to order a prop that matches you engine/trans configuration. The specs that work for fixed props do not work for folding/feathering props, so you really need a professional to size it for you. One important feature you need to assess is the tip clearance, and they can help you with that too.
Frank: Depending on which Yanmar you have there is a slight difference in the max RPM's. Most of the engine were rated at 3600 rpms max. They should be cruised at 70-80% of the max rating (normally 2500-3000 rpm). There are different things that could be wrong, starting with the tach. You may want to have a Yanmar repairman take a look at your engine. As far a prop's are concerned I would be sure that you get the advice of the prop shop to order a prop that matches you engine/trans configuration. The specs that work for fixed props do not work for folding/feathering props, so you really need a professional to size it for you. One important feature you need to assess is the tip clearance, and they can help you with that too.
For 3QM30 series
Frank, I have a service manual for the 2QM20 and 3QM30 series Yanmar engines. According to the performance curves in the manual the engine will deliver 30 HP at 2600 RPM continuously and 33 HP at 2800 RPM for one hour. I think Steve's suggestion to make sure the tachometer is reading right is the place to start. We installed a 3 blade Flex-o-fold (with a 3QM30) and are very pleased with the results. It is interesting to note that our old 3QM30 has a approx. 2 to 1 gear reduction whilst the new 3YM30 can have an approximatley 3 to 1 reduction and revs about 1.5 times higher, implying that the propeller shaft speed would be about the same and therefore the propeller could be re-used with the new engine. Although it is difficult to find calm, still water in the Bay, I estimate that at 1900 RPM we cruise at 5.5 knots with a fuel consumption of about 0.6 gallons per hour. Sailing performance, especially upwind and in light airs, is amazingly better compared to the old 3 blade fixed. John Brecher
Frank, I have a service manual for the 2QM20 and 3QM30 series Yanmar engines. According to the performance curves in the manual the engine will deliver 30 HP at 2600 RPM continuously and 33 HP at 2800 RPM for one hour. I think Steve's suggestion to make sure the tachometer is reading right is the place to start. We installed a 3 blade Flex-o-fold (with a 3QM30) and are very pleased with the results. It is interesting to note that our old 3QM30 has a approx. 2 to 1 gear reduction whilst the new 3YM30 can have an approximatley 3 to 1 reduction and revs about 1.5 times higher, implying that the propeller shaft speed would be about the same and therefore the propeller could be re-used with the new engine. Although it is difficult to find calm, still water in the Bay, I estimate that at 1900 RPM we cruise at 5.5 knots with a fuel consumption of about 0.6 gallons per hour. Sailing performance, especially upwind and in light airs, is amazingly better compared to the old 3 blade fixed. John Brecher
J
Jim Legere
Exhuast Elbow
Carbon deposits accumulate in the exhaust elbow of these old engines, resulting in a loss of power. Might be worth checking - there is lots on this topic in the archives. FYI, my H37C fitted with a 3QM30 with two blade prop cruises at 6.5 knots at 2300 RPM.
Carbon deposits accumulate in the exhaust elbow of these old engines, resulting in a loss of power. Might be worth checking - there is lots on this topic in the archives. FYI, my H37C fitted with a 3QM30 with two blade prop cruises at 6.5 knots at 2300 RPM.
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Frank Bean
Did That
I have taken the engine out and replaced that elbow (since I had the engine out and could). But it was not clogged at that time. Since then Ihave not had a great deal of time to run the engine. Katrina had he on land for a while undoing cosmetic damage. But before I pulled the engine that was what the RPM's indicated, about 2000 -2100 max. I am not near the boat right now but I am wondering if the cable attachment and the throttle adjustment might be limiting my ability to run the engien at higher RPM's. The throttle lever hits the Pedestal guard and that is as high as she will run. Just thinking to myself that might be the issue. If I adjust the cable....that might be the solution. Frank Bean
I have taken the engine out and replaced that elbow (since I had the engine out and could). But it was not clogged at that time. Since then Ihave not had a great deal of time to run the engine. Katrina had he on land for a while undoing cosmetic damage. But before I pulled the engine that was what the RPM's indicated, about 2000 -2100 max. I am not near the boat right now but I am wondering if the cable attachment and the throttle adjustment might be limiting my ability to run the engien at higher RPM's. The throttle lever hits the Pedestal guard and that is as high as she will run. Just thinking to myself that might be the issue. If I adjust the cable....that might be the solution. Frank Bean
J
Jim Legere
Fuel Pump Governor
Frank, Easiest check would be to disconnect the cable at the fuel pump governor on the engine and then move the linkage on the pump by hand and see if you get any more revs. It is a bit tight in there on the side of the engine though. The governor has adjustable stops, but I would suggest that setting up the fuel injector pump is a job for a diesel injector shop (unless you are a diesel mechanic). Good luck.
Frank, Easiest check would be to disconnect the cable at the fuel pump governor on the engine and then move the linkage on the pump by hand and see if you get any more revs. It is a bit tight in there on the side of the engine though. The governor has adjustable stops, but I would suggest that setting up the fuel injector pump is a job for a diesel injector shop (unless you are a diesel mechanic). Good luck.
Make sure the tach is correct
When we had our engine survey the tachometer was reading 300 RPM low at 2400. Don't want to be chasing ghosts or fixing things that aint broke. John Brecher
When we had our engine survey the tachometer was reading 300 RPM low at 2400. Don't want to be chasing ghosts or fixing things that aint broke. John Brecher
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Frank Bean
What can be done?
John, So what was done to correct your low reading tach? Sending unit replaced? New tach? What? Frank
John, So what was done to correct your low reading tach? Sending unit replaced? New tach? What? Frank
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John Brecher
Low reading tach
Frank, I have never fixed the low reading tach. I plan to install a digital unit to replace it some time. I just make a mental note of the difference. For what it's worth my service manual list the following: sender - VDO part number 340.804/007/007 Tachometer - VDO part number 430.230/019/001 This is apparently set to read 0 to 3500 rpm with 126 ring gear teeth. I have not been able to google up any information on these part numbers. John Brecher
Frank, I have never fixed the low reading tach. I plan to install a digital unit to replace it some time. I just make a mental note of the difference. For what it's worth my service manual list the following: sender - VDO part number 340.804/007/007 Tachometer - VDO part number 430.230/019/001 This is apparently set to read 0 to 3500 rpm with 126 ring gear teeth. I have not been able to google up any information on these part numbers. John Brecher
More info needed
Frank, you need to see what sort of tach you have. If it's an electronic one running off the alternator, they have to be adjusted to be accurate. You'd need to take some type of mechanical tach or one of the new hand held electronic tachs and see what the engine speed was, then adjust the tach to match. The observed speed can vary widely (2x, 3x or more) depending on tach type and pully ratios. Someone may have just put the tach on and never calabrated it. If it's a Yanmar tach, it's probably more straight forward and the manual or a Yanmar guy would probably be the way to go.
Frank, you need to see what sort of tach you have. If it's an electronic one running off the alternator, they have to be adjusted to be accurate. You'd need to take some type of mechanical tach or one of the new hand held electronic tachs and see what the engine speed was, then adjust the tach to match. The observed speed can vary widely (2x, 3x or more) depending on tach type and pully ratios. Someone may have just put the tach on and never calabrated it. If it's a Yanmar tach, it's probably more straight forward and the manual or a Yanmar guy would probably be the way to go.
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