What is your mpg, gallons per hour etc... at various speeds?

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sdowney717

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Vessel Name
Old Glory
Vessel Make
1970 Egg Harbor 37 extended salon model
I would like to know some specifics on your engine fuel usage, and also what type hull, displacement, semi displacement, planing, single engine or twin and whether it is gas or diesel.
 
Semi displacement 44' WLL, 47' LOD, 53' OAL
Twin 330 HP Cummins diesels
1.75NMPG at 8 knots
1.5NMPG at 9 knots (thoeretical hull speed)
.75NMPG at 14 knots

440 gallons of fuel
Safe range over 600NM
(Farthest distance in North America between fuel stops 260NM)

These measurements were taken using Floscan fuel computers and are within 10% based on totalizer readings vs actual fuel fill ups over a period of several seasons.
 
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John Deere 4045TFM75 135 HP
45' Semi Displacement 40,000 lbs.
Single Diesel

6.0 knots 1.2 GPH 5.0 NMPG Slow cruise, no wake
7.0 Knots 1.9 GPH 3.7 NMPG Normal cruise, very modest wake
8.0 Knots 3.2 GPH 2.5 NMPG Fast cruise to beat the weather, big wake
9.0 Knots 6.0 GPH 1.5 NMPG Flank emergency only! Surfs up

Ted
 
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Ignorant sailor question....

Are those numbers y'all quoted taken from fuel vs hours calculations or taken from a fuel burn indicator via the engines instruments? Wondering how accurate those engine instruments are....
 
Cummins 6BT5.9 210HP, LWL: 34.7', 31000 lbs, semi-displacement

The following operating hours and ranges are based on continuous running and calibrated fuel flow (FloScan). NM/G and ranges can increase up to 20% assuming 4 hour average daily runs and normal times for warming/cooling.

[FONT=&quot]Really Slow Economy cruise:[/FONT][FONT=&quot] 1400 rpm, 6.2 kts, S/L 1.06, 59.2% propeller efficiency, 28 hp (13% of ME rating), 1.7 gph, 3.7 nm/g, 172 F coolant temp, 380 F pyro, 1.0 lb turbo boost, 195 operating hours with a range of 1207 miles (90%), 74 dba in pilothouse. [/FONT]

[FONT=&quot]Slow Economy cruise:[/FONT][FONT=&quot] 1500 rpm, 6.5 kts, S/L 1.11, 58.8% propeller efficiency, 34 hp (16% of ME rating), 2.1 gph, 3.1 nm/g, 172 F coolant temp, 420 F pyro, 1.5 lbs turbo boost, 158 operating hours with a range of 1024 miles (90%), 77 dba in pilothouse. [/FONT]

[FONT=&quot]Fast Economy cruise:[/FONT][FONT=&quot] 1600 rpm, 6.9 kts, S/L 1.18, 58.6% propeller efficiency, 41 hp (20% of ME rating), 2.5 gph, 2.8 nm/g, 172 F coolant temp, 450 F pyro, 2.0 lbs turbo boost, 132 operating hours with a range of 914 miles (90%), 78 dba in pilothouse. [/FONT]

[FONT=&quot]Slow Fast cruise:[/FONT][FONT=&quot] 1700 rpm, 7.2 kts, S/L 1.23, 57.5% propeller efficiency, 47 hp (22% of ME rating), 2.9 gph, 2.5 nm/g, 173 F coolant temp, 480 F pyro, 2.5 lbs turbo boost, 114 operating hours with a range of 822 miles (90%), 77 dba in pilothouse. [/FONT]

[FONT=&quot]Fast cruise:[/FONT][FONT=&quot] 1800 rpm, 7.5 kts, S/L 1.28, 56.6% propeller efficiency, 55 hp (26% of ME rating), 3.5 gph, 2.1 nm/g, 175 F coolant temp, 510 F pyro, 3.3 lbs turbo boost, 95 operating hours with a range of 709 miles (90%), 74 dba in pilothouse. [/FONT]
 
dhays said:
Ignorant sailor question....

Are those numbers y'all quoted taken from fuel vs hours calculations or taken from a fuel burn indicator via the engines instruments? Wondering how accurate those engine instruments are....
Click to expand...
Newer diesel engines have electronically controlled injection as opposed to the old style mechanically controlled injection. The control is very precise making it easy to calculate theoretical fuel flow as opposed to actually measuring fuel flow. My engine display has a real time fuel consumption display to 1/10 GPH and total fuel consumption counter. On my recent 1,200 mile trip, I kept fairly detailed notes on fuel consumption and fuel purchased. The numbers match well with what the display is telling me. I believe the accuracy is within 2/10 GPH.

Ted
 
Here's what I measured a while back in calm waters. Range in nm is with 10% reserve (1200 gal fuel on board).

1996 John Deere 6068T

1000rpm 4.8kt 4.0nmpg 4300nm
1200rpm 5.7kt 3.2nmpg 3400nm
1400rpm 6.7kt 2.7nmpg 2900nm
1600rpm 7.4kt 2.2nmpg 2300nm
1800rpm 7.9kt 1.4nmpg 1500nm
2000rpm 8.9kt 1.2nmpg 1300nm
2200rpm 9.4kt 0.9nmpg 950nm (WOT)

My "hull speed" is 9.3kt - with a full displacement design and 80,000lb full load the numbers seem reasonable.

In practice I expect that sea state will reduce these numbers. Also currents can be surprisingly large in the ocean (and always against you of course!) I've been following m/v Dirona with interest - and would plan to use a fuel bladder for long ocean passages as they have done. I could easily add 400 gal of fuel that way and give me peace of mind for a long crossing. I hope to go to the South Pacific via Hawaii at some point. I'll need to make 2200nm or so with this plan.

Richard
 
38' LOA 35' LWL 11.8' beam 14000lb wet weight, 450hp Cummins 6CTA

Slow cruise 7.7kt 950rpm 1.9gph

Fast cruise 20kt 2000rpm 11gph

Top end 29kt 2700rpm 24gph

Modified Vee hull, single screw, 1.514:1 gear, 24x23 3b wheel

Slow and fast cruise gph numbers calculated from tank dipstick readings over many trips totalling over 15000nm.

320gal capacity, 1200nm range slow, 545nm fast considering 300gal usable.
 
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dhays said:
Ignorant sailor question....

Are those numbers y'all quoted taken from fuel vs hours calculations or taken from a fuel burn indicator via the engines instruments? Wondering how accurate those engine instruments are....
Click to expand...
My numbers are using my Flo Scan. I don't know how accurate it is - I'll have to run some tests on that before betting my life on the results!

Richard
 
dhays said:
Ignorant sailor question....

Are those numbers y'all quoted taken from fuel vs hours calculations or taken from a fuel burn indicator via the engines instruments? Wondering how accurate those engine instruments are....
Click to expand...

My numbers are from flow scan fuel flow meters.

They are within 10% based on my fuel fill ups vs the readings.
 
After crunching the numbers from our first year, including warm ups & cool downs, anchoring, crabbing, and putzing around with whales and wildlife we averaged 1.3 US gallons per hour.

30' semi displacement, 11' beam, 3.5' draft. Somewhat overpowered...PO replaced original 65 hp with a 100 hp Yanmar 4JH2-UTE.

Usually run at 2700 rpm because it sounds happiest there and make somewhere between 6 and 8 knots (ish) depending on tidal currents.

PO also installed an extra fuel tank for a total of 140 gallons, giving us the ability to roam around in remote areas longer without having to come all the way back in to fuel up.
 
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LWL 46' 4"
LOA 51' 6" (excl swim grid)
Beam 15' 6"
Displacement 23+ tonnes (est from surveyor)

Twin Cummins 555's

1950 rpm 8.8 knots 1.09 nmpg (us gallons)
1800 rpm 7.9 knots 1.35 nmpg (us) 1.62 kmpg (imperial)

800 us gal, 880 - 1000 nmi range

Measured from long runs, tank sight glasses, fill-ups + so pretty accurate.
 
Jay N said:
Cummins 6BT5.9 210HP, LWL: 34.7', 31000 lbs, semi-displacement

The following operating hours and ranges are based on continuous running and calibrated fuel flow (FloScan). NM/G and ranges can increase up to 20% assuming 4 hour average daily runs and normal times for warming/cooling.

[FONT=&quot]Really Slow Economy cruise:[/FONT][FONT=&quot] 1400 rpm, 6.2 kts, S/L 1.06, 59.2% propeller efficiency, 28 hp (13% of ME rating), 1.7 gph, 3.7 nm/g, 172 F coolant temp, 380 F pyro, 1.0 lb turbo boost, 195 operating hours with a range of 1207 miles (90%), 74 dba in pilothouse. [/FONT]

[FONT=&quot]Slow Economy cruise:[/FONT][FONT=&quot] 1500 rpm, 6.5 kts, S/L 1.11, 58.8% propeller efficiency, 34 hp (16% of ME rating), 2.1 gph, 3.1 nm/g, 172 F coolant temp, 420 F pyro, 1.5 lbs turbo boost, 158 operating hours with a range of 1024 miles (90%), 77 dba in pilothouse. [/FONT]

[FONT=&quot]Fast Economy cruise:[/FONT][FONT=&quot] 1600 rpm, 6.9 kts, S/L 1.18, 58.6% propeller efficiency, 41 hp (20% of ME rating), 2.5 gph, 2.8 nm/g, 172 F coolant temp, 450 F pyro, 2.0 lbs turbo boost, 132 operating hours with a range of 914 miles (90%), 78 dba in pilothouse. [/FONT]

[FONT=&quot]Slow Fast cruise:[/FONT][FONT=&quot] 1700 rpm, 7.2 kts, S/L 1.23, 57.5% propeller efficiency, 47 hp (22% of ME rating), 2.9 gph, 2.5 nm/g, 173 F coolant temp, 480 F pyro, 2.5 lbs turbo boost, 114 operating hours with a range of 822 miles (90%), 77 dba in pilothouse. [/FONT]

[FONT=&quot]Fast cruise:[/FONT][FONT=&quot] 1800 rpm, 7.5 kts, S/L 1.28, 56.6% propeller efficiency, 55 hp (26% of ME rating), 3.5 gph, 2.1 nm/g, 175 F coolant temp, 510 F pyro, 3.3 lbs turbo boost, 95 operating hours with a range of 709 miles (90%), 74 dba in pilothouse. [/FONT]
Click to expand...


Jay nice bit of computation reflecting attention to details.

Rough by comparison:
,
27' WL length 10' beam,13,000#(est) 3' draft
-85 hp 4 cyl. Perkins @ 2800 RPM. (In current service-2000 RPM max)
Slow Cruise- 1100 RPM-5.5-5.7 Knot .07-under 1 gallon
Mid Cruise - 1200/1250 RPM- 5.9-6 knot. 1 gallon-1.2 gallon
Normal - 1400/1450 RPM- 6.9-7.2 knot 1.4 gallon
No Max-Self limited to 1400-1450 RPM
 
Ocean Alexander 50 Mk 1, now 60,000lb
Twin John Deere 6068 TFM75 (201HP each)
Fuel capacity: 1240 USG.
Range: adequate :)

For the first 100 hours engines were operated mostly in range of 50-80% power, as required by JD during break-in. For 718nm the average economy was 0.99 nmpg (US gallons). Thus av speed was 7.2 kn.

For the next 400 hours engines have been operated mostly in the range 35-50% power. Thus 2793nm, av economy 1.47 nmpg. And av speed 7kn. Average speeds include idling at dock, and effects of wind & currents.

Graph shows sea trial info for speed vs fuel burn
 

Attachments

  • Speed vs fuel.pdf
    44.4 KB · Views: 67
Small sample size so far but it's interesting to note the smaller boats calculate in gallons per hour and the bigger boats calculate in gallons per mile :D
 
Abbreviated recap:

800 RPM, 6.7 Kts, 2.2 GPH (total), 2.89 NMPG
1200 RPM, 8.9 Kts, 5.8 GPH (total), 1.48 NMPG
2200 RPM, 19.1 Kts, 26.8 GPH (total), .71 NMPG

Twin Cummins 450C (8.3C) diesels, planing hull, approx. 28000-lbs dry, LWL 43' 10.5".

6.7 Kts @ 800 RPM is approx. 1x SQRT(LWL). 8.3 Kts @ 1200 RPM is slightly under 1.34x SQRT(LWL).


2200 RPM is our normal "fast" cruise; although the hull rides slightly better at 2400 RPM (200 "off the top") economy at that rate decreases to approx. .63 NMPG.

Results are estimates from measured speed runs then compared to Cummins' nominal fuel burn curves.

-Chris
 
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1983 Atlantic 30 with 165hp Volvo TAMD40B. Last trip up and down river 72 hrs run time and 84 gallons of fuel-5.8 to 6.5 knts up stream at 1800rpm and 6.5 to 7.8 knts downstream at 1600rpm-that's including 4 hours of generator (4.4 Westerbek) run time.
 
1936 Nunes Brothers Raised Deck Cruiser. 32'8" LOA, 32' LWL, pure displacement, 9,500 lbs displacement.

2011 Volvo-Penta D2-40 diesel (39.6 hp) with a 2.69:1 gear turning a 20: dia x 13.35" pitch 3 blade prop.

6 knots - 1650 rpm - 0.3 gph - 20 nm/gal
7 knots - 2060 rpm - 0.6 gph - 11.7 nm/gal
8 knots - 2650 rpm - 1.3 gph - 6.15 nm/gal

My wife likes to run at a bit under 5.5 knots where fuel consumption is about 0.2 gph for 27.5 nm/gal. She likes that speed because it is quiet. I prefer to run around 7 knots.

Assuming that I consume 90% of fuel capacity my range at 5.5 knots is around 1,000 nm. At 6 knots is it about 700 nm and at 7 knots about 420 nm. Two five gallon jerry cans of diesel in the lazarette increase my range by around 25%.

Numbers based on measured fuel consumption for 6 and 7 knots and calculated fuel consumption from power curve and engine data for 8 knots.
 
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Some of the above data is no doubt accurately measured and some is no doubt wishful thinking. Here is a way to estimate your fuel consumption at displacement speed that will probably be as accurate as anything posted above. Displacement speed is 1.34* sqrt(water line length).


Displacement hull trawlers typically require about 1.5 hp per 1,000 lbs displacement to reach their displacement speed. Semi-displacement trawlers require 2-2.5 hp per 1,000 lbs. The displacement figure was confirmed by plotting the fuel consumption data given in Bebe's book as revised by Leishman. The semi-displacement figures are from my own experience with semi-displacement hulls. They take more fuel because the hull shape is not optimized for low speed.


So take that horsepower and speed and divide the hp by 16 hp per gph. and you will get gph at that speed. The 16 number works pretty good as it is what a Perkins or Lehman will use at 1/4 rated power. And it is what a high output, turbocharged engine will use at 1/10 rated power. A modern John Deere well loaded will probably do a lot better, maybe 18 hp per gph.


Somewhat less accurate is to do the same thing at a sub displacement speed of 1.0*sqrt(LWL). That will result in about half the hp and gph.


David
 
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Nice post David,
I think most just use the hour meter and the #of gallons that goes into the tanks. That of course includes all kinds of running that is not cruise speed and load.

Murray,
I usta cruise my 3HM 35F Yanmar at 2750rpm. I liked it and the Yanmar did too.

Willy is only of average or slightly less than average for efficiency of a FD boat.
1gph
Tad over 6mpg at 6.15 knots.
17,000lbs, 30' OA - 27.5' WLL X 10'6" beam X 3.5' draft.
3000rpm WOT (rated) and 2300 cruise.
2.57-1 BW VD gear w 18 X 13" prop.
 
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djmarchand said:
The semi-displacement figures are from my own experience with semi-displacement hulls. They take more fuel because the hull shape is not optimized for low speed.
Click to expand...

A shockingly effective experiment to illustrate this is to gather some water in a bucket from alongside your semi-displacement vessel while underway, then do the same from directly behind your swimstep.

Dipping the bucket directly aft is like dipping it in a still pond (boat is "dragging" huge amounts of water the same speed of the boat) while doing it alongside might just rip your arm off (boat is moving "through" that water).
 
Slow-planing V hull, 25'7" LOA, 23'4" LWL, 11,000 lb loaded.
Calculated hull speed: 6.46 knots
Single Volvo KAD44P diesel (260hp), duo-prop stern drive.
Diesel capacity 110 gallons.
Yamaha high-thrust kicker (9.9hp), gas capacity 10 gallons.

Fuel usage measured at every fillup over 6,500 engine hours.
Distance traveled from GPS trip log used to calculate nmpg
- very consistent, assuming effect of current averages out.

At 6.0 knots and 1350 RPM, 4.0-4.5 nmpg, calculated gph = 1.33-1.5

At 17.5 knots and 3200 RPM, 1.75 nmpg, calculated gph = 10.0
 
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1.50 GPH 7.5 MPH 2250 RPM Volvo TMD 31 A (100 HP) and NL 5 KW Generator
Fuel capacity 280 gallons 1200 mile range with reserve.
Micro-wake really disappoints wake jumpers.
 
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HiDHo thanks for the (100hp) as those letters TAMD ect ect mean nothing to us not familar w Volvos.
 
Not terribly apropos to this discussion but for a point of comparison...

Sailboat:
LOA: 40.5'
LWL: 30.5'
Displacement: ~22,000 lbs loaded
Yanmar 56hp 4JH4E engine with Autoprop
6 knots: .75 gph
7 knots: 1 gph
Calculated.

Over the past 6 years total fuel consumption has been 1 gph including the use of diesel furnace and time spent motor sailing.
 
djmarchand said:
Displacement speed is 1.34* sqrt(water line length).

Semi-displacement trawlers require 2-2.5 hp per 1,000 lbs.

So take that horsepower and speed and divide the hp by 16 hp per gph. and you will get gph at that speed.

Somewhat less accurate is to do the same thing at a sub displacement speed of 1.0*sqrt(LWL). That will result in about half the hp and gph.
Click to expand...


Good post.

FWIW, I talked myself into always interpreting 1.34 x SQRT(LWL) as a theoretical "maximum" displacement speed. As opposed to a mandatory or target speed.

In our case, I think an estimated 2.89 NMPG @ 1.34etc versus an estimated 1.46 NMPG at 1.00etc is a useful illustration.

Given that I only have the manufacturer's fuel flow curves to work with, I can only estimate... but at least long-term usage suggests their nominal curves are in the ballpark on our boat.

If I understand your semi-displacement formula correctly, our 28000-lbs * 2.5 = 70 and 70/16 says 4.375 GPH at our 1200 RPM 1.34etc speed. (Assuming that somewhat works for planing hulls, too.) I'd be happy to learn our burn rate is closer to 4.375 GPH (~2.03 NMPG) at that speed of 8.9 kts, versus our current estimate of 5.8.

I'm installing new digital fuel gauges in a few weeks, so hope use those to tweak my current estimates. Still won't be Flowscans, but incrementally better than what I've got for measurement now.

-Chris
 
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dhays,
Ten foot overhang? Wow. Is she an old boat? S/L ratio does wonders. Your 40' boat weighing several tons more than my 30' boat and burning a quart less fuel at the same speed. Your WLL is only 3' longer than mine but it sure delivers. This is a good lesson for all re SLR ... Speed Length Ratio.
 
manyboats said:
dhays,
Ten foot overhang? Wow. Is she an old boat? S/L ratio does wonders. Your 40' boat weighing several tons more than my 30' boat and burning a quart less fuel at the same speed. Your WLL is only 3' longer than mine but it sure delivers. This is a good lesson for all re SLR ... Speed Length Ratio.
Click to expand...


My bad. A typo. LWL is 36.5'

Sorry. Too late to edit the post as well.
 
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