I know this has been discussed before. But I am looking for some who has checked it out on a 3870 with twin 130 Chry. Mit. diesel engines. What is the best speed to use the least amount of fuel running both engines without the gen set, and running both engines with the gen set. The boat is a 1985 model.
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On ANY boat the most efficient speed will be slow.
Look back at your wake. Think of the wake as wasted energy.
KEVIN SANDERS
4788 DOS PECES - SEWARD ALASKA - LA PAZ BCS MEXICO
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According to David Gerr in his book "Propeller Handbook", the most fuel efficient speed is about 3/4 of the hull speed. This is about equal to the square root of the water line length in feet with the answer in knots. For a 38xx that would be six knots or seven mph. On flat water you might achieve up to four mpg.
Your generator will probably burn about a quart and hour at light load.
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If you have an 8KW gen set, it will burn about 3/4 gal per hour fully loaded.rbmitchell wrote:
According to David Gerr in his book "Propeller Handbook", the most fuel efficient speed is about 3/4 of the hull speed. This is about equal to the square root of the water line length in feet with the answer in knots. For a 38xx that would be six knots or seven mph. On flat water you might achieve up to four mpg.
Your generator will probably burn about a quart and hour at light load.
Started boating 1965
Bayliners owned: 26 Victoria, 28 Bounty, 32, 38, and 47 since 1996Comment
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Probably the best way the see that is a good hull speed calculator.rbmitchell wrote:
.. the most fuel efficient speed is about 3/4 of the hull speed. This is about equal to the square root of the water line length in feet with the answer in knots.
This is my favorite: https://"http://www.psychosnail.com/...EED CALCULATOR
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In my short time (1 yr.) with my 3870, running Mits engines, I found that around 1800 rpm, 8.5 knots gives me a good balance between fuel consumption & "time to get there". At that speed/rpm, getting about 2 nm/gal. If you slow it down as the previous posts suggest to about 6 kts, you'll be running about 1200 rpm and getting about 4 nm/gal.
Hope this helps.
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