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05-11-2021, 07:08 PM
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#1
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Member
City: SOUTH HAMILTON
Join Date: Nov 2020
Posts: 8
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IG 36 cruise speed vs fuel burn
I have a IG 36 with twin cummins 270hp, anyone have similar? Curious about fuel burn at different cruising speeds. Any info is greatly appreciated!
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05-11-2021, 08:19 PM
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#2
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Senior Member
City: Brisbane
Vessel Name: Malagari
Vessel Model: Island Gypsy 36 Europa
Join Date: Mar 2015
Posts: 422
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Wow2 - thats a bit of grunt you have down in the engine room - we have two good old boys - Ford Lehman 135s- I calculate about 16Litres per hour total @1700rpm so you may be able to extrapolate from that
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George
Brisbane
IG 36 Europa
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05-11-2021, 08:27 PM
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#3
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Member
City: SOUTH HAMILTON
Join Date: Nov 2020
Posts: 8
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I will say I feel that my power is a bit excessive which is why I'm curious if anyone else has similar. Thank you for the reply!
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05-11-2021, 09:44 PM
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#4
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Guru
City: Sydney
Vessel Name: Sojourn
Vessel Model: Integrity 386
Join Date: Oct 2011
Posts: 13,293
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Jono, is that a repower?
I had an IG 36 with more than adequate Lehman 120s which used 12-16L p/hour total at around hull speed.I know of 200hp Volvos factory fitted to 36s.
My IG36 based Integrity 386 has Cummins 210s(yea,no aftercoolers!) and seems quite economical. The Qld. Integrity 426 I didn`t proceed with had C 270s and hit 17 knots on sea trial.
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BruceK
2005 Integrity 386 "Sojourn"
Sydney Australia
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05-12-2021, 06:07 AM
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#5
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Valued Technical Contributor
City: Litchfield, Ct
Join Date: Aug 2012
Posts: 6,775
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You can easily prepare a fuel burn yourself with no instruments. Print out the attached data sheet for your engine and particularly note the third graph- engine rpm vs fuel consumption.
Then take your speed at various rpms and make another graph by plotting speed vs fuel consumption from the rpm graph times two. It should be within 10-15%.
Another way is to join boatdiesel and use their prop calculator. But that is totally theoretical whereas the above method at least uses your real world speed vs rpm data.
You can obtain fuel burn reports from fellow TF members, but in my experience they are highly variable and don't take into account generator use, currents and are often just guesses.
David
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05-12-2021, 06:30 AM
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#6
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Guru
City: Aventura FL
Vessel Name: Kinja
Vessel Model: American Tug 34 #116 2008
Join Date: Oct 2017
Posts: 10,595
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Quote:
Originally Posted by Jono57766
I will say I feel that my power is a bit excessive which is why I'm curious if anyone else has similar. Thank you for the reply!
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Jono, create your chart. RPM, SOG reading from you very own meter, GPH, then you can figure max. distance/RPM.
Anything someone else provided may not be accurate for your boat due to weight, sea state etc.
To negate the current etc, 2 mile out, 2 miles back. You can refine the chart over time.
Do this w/o the generator running then figure in about 1.5gph.
__________________
Two days out the hospital after a week in the hospital because of a significant heart attack.
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05-14-2021, 01:13 AM
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#7
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Hospitality Officer
City: Pittwater
Vessel Name: Sarawana
Vessel Model: IG 36 Quad Cabin
Join Date: Sep 2010
Posts: 1,896
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I can't add too much to this conversation as I have the same FL120 configuration as Bruce's old boat. Except to say that I did a graph as discussed above and noted that that the fuel consumption on our IG 36 increased 90% when measured against our cruising speed at 1600rpm to WOT (2600rpm). All for a gain of 1.8 knots!
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05-14-2021, 04:59 PM
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#8
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Guru
City: Seattle
Vessel Name: AZZURRA
Vessel Model: Ocean Alexander 54
Join Date: Aug 2017
Posts: 4,281
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With that much HP on a 36’ boat you might be able to go 20kts at a gallon a mile. You will probably use one two two tenths more gallons per hour over the guys with the Lehman’s if you match their speed.
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05-14-2021, 07:55 PM
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#9
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Valued Technical Contributor
City: Litchfield, Ct
Join Date: Aug 2012
Posts: 6,775
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Quote:
Originally Posted by tiltrider1
With that much HP on a 36’ boat you might be able to go 20kts at a gallon a mile. You will probably use one two two tenths more gallons per hour over the guys with the Lehman’s if you match their speed.
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Why more fuel for the Cummins? The Cummins has the same displacement as the Lehman, so the mechanical parasitic losses should be the same. The turbo on the Cummins might actually improve efficiency a bit, even at low rpms as well as more modern injectors.
David
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05-14-2021, 08:06 PM
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#10
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Guru
City: Sydney
Vessel Name: Sojourn
Vessel Model: Integrity 386
Join Date: Oct 2011
Posts: 13,293
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Quote:
Originally Posted by DavidM
Why more fuel for the Cummins? The Cummins has the same displacement as the Lehman, so the mechanical parasitic losses should be the same. The turbo on the Cummins might actually improve efficiency a bit, even at low rpms as well as more modern injectors.
David
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. I have not done the figures but my impression, watching the sight tubes etc, is that the turbo Cummins 210s in a boat with hull very similar/derived from the IG36, look to be more economical than the L120s even at slightly faster speed.
__________________
BruceK
2005 Integrity 386 "Sojourn"
Sydney Australia
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05-15-2021, 12:40 AM
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#11
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Guru
City: Seattle
Vessel Name: AZZURRA
Vessel Model: Ocean Alexander 54
Join Date: Aug 2017
Posts: 4,281
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Quote:
Originally Posted by DavidM
Why more fuel for the Cummins? The Cummins has the same displacement as the Lehman, so the mechanical parasitic losses should be the same. The turbo on the Cummins might actually improve efficiency a bit, even at low rpms as well as more modern injectors.
David
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That is very possible. I thought the Cummins was a bigger displacement engine. If you are correct then the tenth might go the other way. My main point was no significant difference in fuel consumption.
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05-15-2021, 07:16 AM
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#12
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Guru
City: Toms River
Vessel Name: V E N T U R E
Vessel Model: 1996 36' Island Gypsy Classic
Join Date: Dec 2009
Posts: 1,361
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Our IG 36 has twin Cummins 210hp. With light boat--less than half fuel and water we can do 14knots. So you should easily do 15 in any load conditions. We cruise 1150 rpm at 7.5 knots burning 3 gallons per hour total--no genny running. At this relaxed pace the boat runs very quietly--sound level is so low it is amazing. Is running this slow good for the engines? They are 25years old and not causing any issues so I am not overly concerned. With my 410 fuel cap I have close to 1ooo mile range. I have two wing tanks and a 90 gallon center tank. When the wing tanks are approx one quarter fuel I have transfer system to drain the tanks thru a filter into the center tank as a day tank. This way I can use all available fuel if needed.
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