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Old 29-08-2009, 15:53   #1
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Diesel Consumption - Volvo D2 - 55hp

I am having a new 220 litres tank installed as well as a new Volvo D2 55 on my 38' sailboat.

Would someone please clarify to me what's the approximate fuel consumption of a Volvo D2-55 shaft propeller drive no more than 2,200 rpm, max speed 6 knots?

The way I read the fuel consumption curve on the Volvo pamphlet at
http://www.marinedieseldirect.com/re...d2_55_55hp.pdf
indicates over 5 litres per hour.

The mechanic insists it is more like 2 litres per hour

Thank you!

Paolo
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Old 29-08-2009, 16:16   #2
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here are some consumption figures for an HR40/56 hp yanmar. You can expect something similar. It all comes down to waterline lenght, disp and the load on the engine, in particular correct prop sizing. You will note at full power consumption will be around 10 lph
go to
http://www.hallberg-rassy.com/yachts/hallberg-rassy40,
scroll down to documents and select fuel consumption
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Old 29-08-2009, 17:16   #3
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200 grams per horse power, probably less for D2 if run at optimum ("economy") rpms

go into the hp/rpm table with the rpms, read the power generated, multiply

they also give the exact data in the leaflet (available online)

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Old 29-08-2009, 18:16   #4
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Thank you, barnakiel.
This is where I get confused. I have the Volvo Penta D2-55 pamphlet with Fuel Consumption offered in two graphs, At Full Load and At Calculated Propeller Load exp.3 (?).
At 2200 rpm the lower graph shows 5 liters/h. The upper graph shows 9 liters/h. The notes offer no clues.

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Old 29-08-2009, 19:19   #5
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At full load and 2200 rpm = 8 liters per hour. But imagine now that you unload the engine (put the gear into neutral) and then rev it up to 2200 rpm. Will it burn more / less? Imagine you are running at 120 steps per minute and then you do the same but fully loaded up say with a heavy rucksack. When will you burn more energy (use more fuel)?

Hence the second curve which allows for this phenomenon. From this curve you learn 5 liters is what you might expect, say in flat water, while under more load the consumption may go all the way until 8 liters. Even more load and the engine will get 'overloaded' and start to smoke!

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Old 29-08-2009, 20:29   #6
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Fuel consumption

Quote:
Originally Posted by barnakiel View Post
At full load and 2200 rpm = 8 liters per hour. But imagine now that you unload the engine (put the gear into neutral) and then rev it up to 2200 rpm. Will it burn more / less? Imagine you are running at 120 steps per minute and then you do the same but fully loaded up say with a heavy rucksack. When will you burn more energy (use more fuel)?

Hence the second curve which allows for this phenomenon. From this curve you learn 5 liters is what you might expect, say in flat water, while under more load the consumption may go all the way until 8 liters. Even more load and the engine will get 'overloaded' and start to smoke!

b.
This is quite clear.

Because the new tank is 220 litres, under average load I can expect only ~36 hrs autonomy.

Many thanks again.

Paolo
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Old 30-08-2009, 10:05   #7
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To some extent it depends on the hull of your 38 footer.

A modern 41 will displace some 7-8 metric tonnes, an older design easily twice this amount. You need roughly 2 hp / t to drive the hull at econo speed (where consumption per mile is lowest) this would mean some 15-20 hp times 200 grams say 3.5 liters per hour and probably at around 5.5-6.5 knots. This makes possibly 60+ hours on a tank = 350-400 Nautical miles on one tank.

Now the heavier boat will burn twice the amount and end up with half the range. Since you have a 53hp engine in a 38 footer I am lead to imagine that your boat is mid- or heavy displacement.

To extend you range you can be looking for the rpm / speed where consumption per mile is lowest - sometimes it is actually rather slow and many skippers decide to shorten the range but go at slightly higher speed / spend less time on the passage. If this is the case then your engine is matched well and it will be properly loaded which is always good for the longevity of the engine (diesels hate to be run under light loads).

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Old 30-08-2009, 16:01   #8
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Fuel consumption

Well, you have a tremendous knowledge, and in this case quite reassuring.

Should we go for longer cruises across areas without possibility of refuelling, there will always be the portable, soft tank option.

Will let you know, in any case, as soon as I get my boat back, what's the actual consumption in diverse conditions of use.

Thank you again.

Paolo
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Old 30-08-2009, 17:24   #9
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I only have the knowledge that I read from the leaflets and some general books (Calder is good on engines and things electrical).

Happy sailing!
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