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1 litre of diesel every 8 seconds


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Rigger is correct

The old rule of thumb for diesels was 20horsepower-hours/gallon

450l/hr is 100 gallons/hr so that is 2000hp or thereabouts

Modern engines are more efficient so probably a little more than 2000hp.

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As a bench mark, most of the Riv owners here (around 38 foot) do 100 litres an hour. Half the speed half the fuel, so the average is the same over distance.

The fusion 40 power cat 44 an hour but ten knots slower than the Rivs (the power cat does 22 knots).

The ex PT boat, that is being switched back to twin petrols from smaller diesels, for the hell of it (65 + feet) about 600 litres an hour !!!

He apparently has good mates that will chip in for a blast....(close to 37 knots on smooth water)

The bigger semi,s , 45 feet or so about 200 +

The sleek Italian job (40) about 180.

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Me ? 3.8 litres an hour.

Isuzu industrial. 53 HP.

38 feet. Medium weight cruising boat. (For a steel boat), or very heavy (by 3.5 tons) compared to a plastic.

Clean bum around 7.2 knots. No push or pull.

point 6 of a knot above hull speed.

From my expirience people are a little bit lose with their boat speed and fuel economy.

In particular, I have found that speed under motor, into strong head ways have been very badly exagerated.

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Mate of mine just bought a Maritimo 55 with $6000 of diesel in the tanks. An identical boat we were on at Easter recorded by the time he got back to Tauranga after a Easter gulf cruise he'd be up for $7500 to top the tanks up for winter. (he's now relocated the boat to Auckland)

 

Big bucks to run those things.....

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Modern engines, it's all about grams of fuel per HP hour. This is engine efficiency. Then how many HP, how much displacement etc etc, related to speed, then that can give Litres per Nautical mile.

 

The Rivs etc are very heavy, and often have lots of HP. You pay for the total mass in fuel consumption.

 

For example, my bros boat is 44 ft LOA. Has a Scania DI9 - 500 hp. uses 80-90 grams/hp hour. Usually works out about 58 Litres/hour at around 20 -23 knts (conditions and load dependent) - approx 2.9 litres per hour. The boat is considered light (under 10,000 kg) and very economical by all his launch mates....some of which have vessels that use up to 290 Ltrs/hr for the same performance.

 

I reckon filling the boat once to capacity (1700ltrs) is more fuel than I've used in the last 5 years, INCLUDING a 20,000 mile voyage... :shock:

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I once spent a number of years working on a Ski Race boat that burned close to those numbers. Only 21 ft and would blow 400 litres in an hour at full noise. Luckily the silly skiers out back couldn't hold the boat at full throttle so a race would normally be a little more economical than that. They would still be pulling over 200 kph on the straights though.

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80ft and that was at 18kn, Big Italian fizzy boat POS.

 

Italian you say? So even more concerning would be the oil consumption, surely!

 

Have you ever know an Italian motor to run long enough to consume oil ?

The electric's would stop that

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YEP, and when my motor cruisers friends give me that fourth drink look, N say..."so whats ya rags worth mate ? ",..wink wink..

I have another sip of mine and reply..."hmmm ya havnt taken ya boat out for a spin lately"....

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