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Old 05-02-2013, 20:40   #1
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Fuel Consumption

what 40-100 horse diesel engine has the best gallons per hour
how many g/h does a perkins 4107 use at idle and hull speed?
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Old 05-02-2013, 20:49   #2
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Re: fuel consumption

Don't know if this will help but my Perkins 104.22 50hp averages 3 litres per hour at about 6knts The boats about 12 tons.
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Old 06-02-2013, 05:40   #3
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Re: fuel consumption

40 to 100 horse power engine are almost all mechanically injected so they all use about the same fuel- within 5% to produce the same horsepower. To answer your question about fuel consumption to reach displacement speed we need water line length and displacement values.

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Old 06-02-2013, 14:39   #4
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Re: fuel consumption

Drousy,

Figure a reasonably efficient diesel (all of them) will burn about .33-.35lb/(hp * hr). Until you get into ships engines (read thousands of hp), there isn't much efficiency difference. The major difference is that an engine operating at a higher percentage of its maximum output will be slightly more efficient since the overhead costs (moving the driveshaft, and powering the alternator, ect) become a lower percentage of the net output.

The amount of hp your boat needs to hit a given speed is a function of the prop, hull design and weight not the engine.
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Old 08-02-2013, 18:48   #5
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Re: fuel consumption

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Originally Posted by Stumble View Post
Drousy,

Figure a reasonably efficient diesel (all of them) will burn about .33-.35lb/(hp * hr). Until you get into ships engines (read thousands of hp), there isn't much efficiency difference. The major difference is that an engine operating at a higher percentage of its maximum output will be slightly more efficient since the overhead costs (moving the driveshaft, and powering the alternator, ect) become a lower percentage of the net output.

The amount of hp your boat needs to hit a given speed is a function of the prop, hull design and weight not the engine.

im asking about the fuel economy not the horsepower. how much diesel does your engine burn at idle?
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Old 08-02-2013, 19:26   #6
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Re: fuel consumption

I very seldom let my engine Idle! except for the warm up period of about 10 minutes!! even for charging, and refer I don't use an Idle , but run her up to at least 1000 to 1200 rpms, Idle speed is mostly between 600 to 850 rpms on most diesels. Ive found I get better fuel burn at those slitely higher rpms. just my 2 cents
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Old 08-02-2013, 19:32   #7
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Re: fuel consumption

fuel consumption on a Perkins 4-107 ... and I can now pass on my findings ...

General cruise speed of 40% throttle and about 4 - 5kts calm water = 2.5 - 2.8 litres per hour.

Knock back the lever a touch to about 30 -35% throttle ... losing about 0.5kts and the consumption drops dramatically to 2 - 2.5 litres per hour.

Increase to 60% or more then we get 3.0 or more litres per hour .... with flat out 9.0 kts giving about 4 litres per hour - with an estimated 15% + wastage of fuel as unburnt judging by the crud thrown out of exhaust.

The other week-end we motored for approx. 7.5 hrs and used approx. 20 litres and that included a good %age of time into heavy short wave seas with boat pitching heavily ....

So there we are .... I know know what to expect from my 250 quid second-hand "bargain" motor .... Perkins 4-107 estimated 42HP.
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Old 08-02-2013, 21:14   #8
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Re: fuel consumption

i have a perkins 4-108 on a 20000lb cutter - cutaway full keel.

i don't idle long enough to have any idea what it burns at that rpm. at cruise rpm - usually 1700 - i use about 3 quarts per hour. i've calculated this from over nine years of engine logs.
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Old 08-02-2013, 21:15   #9
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Re: fuel consumption

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Originally Posted by Cotemar View Post
fuel consumption on a Perkins 4-107 ... and I can now pass on my findings ...

General cruise speed of 40% throttle and about 4 - 5kts calm water = 2.5 - 2.8 litres per hour.

Knock back the lever a touch to about 30 -35% throttle ... losing about 0.5kts and the consumption drops dramatically to 2 - 2.5 litres per hour.

Increase to 60% or more then we get 3.0 or more litres per hour .... with flat out 9.0 kts giving about 4 litres per hour - with an estimated 15% + wastage of fuel as unburnt judging by the crud thrown out of exhaust.

The other week-end we motored for approx. 7.5 hrs and used approx. 20 litres and that included a good %age of time into heavy short wave seas with boat pitching heavily ....

So there we are .... I know know what to expect from my 250 quid second-hand "bargain" motor .... Perkins 4-107 estimated 42HP.

thx alot thats exactly what i was looking for. i wish i was at your level already.
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Old 09-02-2013, 15:57   #10
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Average a tad over 3 liters per hour with 65 hp naturally aspirated cummins. That's over weeks. Usually try for 5 knots plus when motoring
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Old 09-02-2013, 16:43   #11
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Re: fuel consumption

A marine diesel engine consumes about 1 gallon per hour (GPH) for every 18 hp generated

Another way to calculate the amount of diesel fuel used (gallons) in 1 hour is to multiply the horsepower being used by 0.055.

or

For petrol engines fuel consumption can be estimated as:
Litres/hr = 0.508 x KWprop
For diesel engines fuel consumption can be estimated as:
Litres/hr = 0.274 x KWprop

Where: KWprop = Kilowatts from propeller power curve
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Old 09-02-2013, 16:49   #12
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Re: fuel consumption

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Originally Posted by sabray View Post
Average a tad over 3 liters per hour with 65 hp naturally aspirated cummins. That's over weeks. Usually try for 5 knots plus when motoring
More info here would be appreciated please, a few questions:
Are they B3.3's?
RPM to get the 5+ knots?
Approx Fuel usage at full noise?

Thanks
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Old 09-02-2013, 17:06   #13
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Re: fuel consumption

Perkins 4.108, motoring at 1500 RPM's, 6 KTS, .7 gallons per hour. I don't idle for enough hours to tell you that.
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Old 09-02-2013, 17:36   #14
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Re: fuel consumption

this is how I am calculating cruising speed of my FNM HPEP 190 diesel. this way you can calculate any speed, from idle to wot

cruising speed 3250 rpm 160hp/1118kw

220g/KWh x 118KW = 259600 g/h or 25.960 kg/h

0.85 kg/l is a typical figure for diesel

25.960 L/h : 0.85 = 30.5 L/h = 8 US gallons/h
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Old 09-02-2013, 17:45   #15
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Quote:
Originally Posted by cat man do View Post

More info here would be appreciated please, a few questions:
Are they B3.3's?
RPM to get the 5+ knots?
Approx Fuel usage at full noise?

Thanks
Yes 4b3.3 cummins. Pushing 30,000 lbs mono. Usually at near 2200 rpm we see 5 knots plus with 17 inch prop. Pushing at high rpm 2500 I would expect. 4.75 litres per hour. The curves are pretty good from most manufacture.
If that helps.
I really like my cummins. Cause its been well behaved. No odd failure so far. Starts runs and waits. Then it starts runs all over again.
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