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Old 09-12-2015, 06:27 AM   #1
gaston's Avatar
City: Sydney
Country: Australia
Join Date: Jul 2015
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Is it possible or have I got things wrong

Topped up the boat today (Perkins 6 cylinder 120HP ) 76 liters and 24 hours engine run time mostley running at 1000 to 1400rpm @ 6/7.5k knots thats only 3.2 liters a hour Am I dreaming

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Old 09-12-2015, 07:37 AM   #2
City: Satsuma FL
Country: United States
Vessel Name: No Mo Trawla
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Sounds right to me. We burn a little more than that at 1650 rpms on a 135hp 6-354 with a 38' boat.

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Old 09-12-2015, 07:43 AM   #3
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City: Marathon, Florida
Country: USA
Vessel Name: Walkabout
Vessel Model: 1978 Marine Trader 36
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Something does not seem right. 1000 - 1400 rpms to get 6/7.5 knots? Must have been a good current. 1000 is just above idle. We have an FL 120. The manual says to operate between 1250 and 2500 rpms. We usually run at 1450 which is the peak of the torque curve. I have been told that is the most economical rpm (top of curve) to run a diesel. I don't know if that is true but makes sense to me. Our speed at 1450 is 6 knots.
"Whenever you find yourself on the side of the majority, it is time to pause and reflect." Mark Twain

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Old 09-12-2015, 08:51 AM   #4
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City: Essex, Ct
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That is rather low. That fuel burn implies you were producing about 15 hp. It might be possible at 6 kts but not at 7.5 kts.

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Old 09-12-2015, 09:32 AM   #5
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City: Bass Harbor
Country: USA
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Impossible to say without knowing a bit about your boat - displacement. waterline length, etc. As far as your engine rpms are concerned without knowing the above and the details of your transmission (gear ratio) and prop (diameter, pitch, # of blades, etc), no one can make a meaningful comment.
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