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Old 02-01-2010, 14:58   #1
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Average Fuel Usage for 38'ers

Please forgive my ignorance , I am a new member , and am extremely keen to learn as much as possible before purchase .
Im looking at a Cat in the 38ft range .
I have had some confusion with fuel burn amounts .
eg Lagoon claim to use 3lt/hr while Leopard owners are claiming closer to 7lt/hr.
Have I got this right , or are the lagoon threads Ive read possibly refering to per side .
Im not only looking at Lagoon or Leopard , but these are more recognized .
Does anyone know the fuel economy of a few known 38ft cats . I certainly dont want to disregard Leopard if I am simply confused. But that fuel usage would be considered to high for my liking, not that I intend to motor everywhere of course but still is a consideration with our much higher fuel prices here in Aus.
Hope you can help and look forward to hearing from you.
Regards , cheers Darren
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Old 02-01-2010, 16:34   #2
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Quote:
Originally Posted by Mate View Post
Please forgive my ignorance , I am a new member , and am extremely keen to learn as much as possible before purchase .
Im looking at a Cat in the 38ft range .
I have had some confusion with fuel burn amounts .
eg Lagoon claim to use 3lt/hr while Leopard owners are claiming closer to 7lt/hr.
Have I got this right , or are the lagoon threads Ive read possibly refering to per side .
Im not only looking at Lagoon or Leopard , but these are more recognized .
Does anyone know the fuel economy of a few known 38ft cats . I certainly dont want to disregard Leopard if I am simply confused. But that fuel usage would be considered to high for my liking, not that I intend to motor everywhere of course but still is a consideration with our much higher fuel prices here in Aus.
Hope you can help and look forward to hearing from you.
Regards , cheers Darren

You may find it depends on the size of the motors, and whether you are thrashing into the weather or running from it.
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Old 02-01-2010, 17:07   #3
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Our Privilege 39 has Yanmar 3GM30F engines (1990 vintage), which are 3-cylinder fresh-water cooled. They burn a pretty consistent 1/2 gallon per hour per engine...
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Old 02-01-2010, 18:25   #4
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All diesels are similar - about 200 gr/hp/hour used. You can judge the hp from how many revs you make (there is a rv / hp chart in engine's specs).

Example:
- 10 hp engine at full revs = 2 ltrs / hr
- same engine at half revs (look up the engine graph, say it is 5 hp at half revs) = 1 ltr per hour

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Old 02-01-2010, 18:57   #5
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Thanks guys , anymore info is always good.
I am trying to get an average fuel usage in average conditions , doing an average cruise speed of 6-7 knts. Im thinking this is about the optimum cruise speed and would think most cats could cruise / motor at this speed confortably.
Im mainly thinking this way because the first few years of cruising for me will be weekends and weeks only, so time will not necessarily be in my favour eg , one motor , less speed , less fuel. NO wind.
Thanks again , Im very curious about the Leopard burn , seems alot .
Cheers Darren
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Old 02-01-2010, 19:09   #6
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If your engines are modern enough then you can get a digital fuel flow/clock/speed meter that will tell you where the economy speed is. No need to guess.

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Old 03-01-2010, 02:54   #7
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Using a 30 HP Lombardini during 6 days from the Azores to the gulf of Biscaye ( no wind at all ) we burned 2.5 liters per hour at 6 knots one engine running all the time.
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Old 03-01-2010, 04:58   #8
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Fastcat , 2.5lt at 6 knots , thats pretty good. If you run both motors and drop the revs can you achieve the same speed ?
Not to get off the subject of fuel burn because it is of importance to what I purchase , so please keep the info coming .
But , how well does a cat handle running one motor , or one side . Does it put extra stress on other parts eg , rudder etc.
I still think the economy of the Leopard 38 to be high , why do they have such big hp compared to others the same size, (the older ones anyway)my only thought is because they were primarily for charter and maybe motoring more so less stress on larger motors. My thoughts only , dont realy have a clue. Got so much to learn , and loving every minite of it .
Cheers Darren
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Old 03-01-2010, 05:40   #9
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Hallo Darren, yes off course you can run both motors with lower revs to achieve the same speed but fuel economy suffers big time , same speed 2 motors running 3.5 liter per hour or about 40 % higher fuel consumption and more noise.It handles well with one motor, harbor maneuvering is tough with only one motor running but can be done.
Larger motors come in handy with strong wind on the bows, the windage is high on cats.
In general one can say that a catamaran needs about 6 hp per metric ton loaded weight and that will be enough in most conditions.
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Old 03-01-2010, 05:48   #10
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On our Sunstar with Yanmar 3gm30's we burn .5 gallons per hour per motor. Under 1 motor the speed is mid to upper 6's. under both motors mid to upper 7's.
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Old 03-01-2010, 08:51   #11
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Quote:
Originally Posted by Mate View Post
Please forgive my ignorance , I am a new member , and am extremely keen to learn as much as possible before purchase .
Im looking at a Cat in the 38ft range .
I have had some confusion with fuel burn amounts .
eg Lagoon claim to use 3lt/hr while Leopard owners are claiming closer to 7lt/hr.
Have I got this right , or are the lagoon threads Ive read possibly refering to per side .
Im not only looking at Lagoon or Leopard , but these are more recognized .
Does anyone know the fuel economy of a few known 38ft cats . I certainly dont want to disregard Leopard if I am simply confused. But that fuel usage would be considered to high for my liking, not that I intend to motor everywhere of course but still is a consideration with our much higher fuel prices here in Aus.
Hope you can help and look forward to hearing from you.
Regards , cheers Darren
Good Day Mate,

If you are Australian or in Australia, please look at Australian designs, there is more variety than any where else in the world. Be aware that the designs you are looking at are primarily for charter use and are in the main heavy for size.

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Old 03-01-2010, 10:04   #12
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Running one engine then giving it a break when running the other I believe a common practice on cats. Have not heard any issues related to stress or anything. Service, oil check-up etc. -wise you can't beat it. One of great advantages of a cat over most monos.

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Old 03-01-2010, 10:10   #13
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"Our Privilege 39 has Yanmar 3GM30F engines (1990 vintage), which are 3-cylinder fresh-water cooled. They burn a pretty consistent 1/2 gallon per hour per engine... " Yep, our Lagoon 42 with the same engines burned about the same amount as that, boat was very heavily loaded also... if the wind was blowing harbor manuevering with one engine would not work. I would have liked a little more horsepower personally, although the boat moved along well in all sea states... If your builder offers a little larger engines I would seriously think about them. The fuel penalty would be very small...
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Old 03-01-2010, 11:21   #14
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more sunstar fuel figures ....

Quote:
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On our Sunstar with Yanmar 3gm30's we burn .5 gallons per hour per motor. Under 1 motor the speed is mid to upper 6's. under both motors mid to upper 7's.
My 10hp v/pentas use 1 litre per hour each and can scoot along at 5 knots using only 1 engine . 2x engines = 2.5 litres per hour at 7 +knots
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Old 03-01-2010, 13:59   #15
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Gidday again , These are the sorts of figures I thought I was reading and make cat ownership all the more appealling for cruising . To me.
Why would the leopard then be so high , one spec I read said 2 gallens per hour . In my turms thats over 7.5ltr / hr , far to high . Are there any leopard owners who can verify my findings. I may contact the owner if posible and make sure it wasnt just a typing error.
Keep it coming , I find this very interesting.
Thanks for all your comments so far , cheers Darren
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