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Old 17 November 2012, 19:14   #1
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kms per litre

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Greetings form Sydney Australia
A few months ago I purchashed my 5.5 metre Gemini with a 115hp fuel injected Johnson. 100 hours. To date we have been doing some half day trips around Sydney Harbour, broken Bay and some tubing and Wakeboarding on the Hawkesbury river. All great fun however after reading RIB magazine and getting a feel for the recretaional use of RIBs in the UK I am now keen to go outside and potentially do some Island camping. Broughton Island of Nelson bay looks "choice". Problem is I have no idea how many Kms I should be able to get out of the 75 litre, 20 Gallon tank. Any ideas?
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Old 17 November 2012, 19:27   #2
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Safe bet would be 1 mile lt or 1.6 k per lt if that helps allow. 20 0/0 reserve
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Old 17 November 2012, 22:16   #3
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Quote:
Originally Posted by falcon0310
Safe bet would be 1 mile lt or 1.6 k per lt if that helps allow. 20 0/0 reserve
So 75 litres @1.6 per km is about 46 kms range. What do you mean by 20 reserve?
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Old 18 November 2012, 02:23   #4
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1.6 km per lt = 75l x 1.6km = 120km TOTAL range , NO RESERVE

look at the REAL fuel consumption of your motor under different conditions like load , speed , sea conditions .
A GPS will record the distance during the trip and the petrol station gives you the liters after refilling .
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Old 18 November 2012, 04:22   #5
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I agree with 1.6km per litre as a sensible planning figure. If it is a modern four stroke (presumably the Johnson equivalent model to the Suzuki DF115) then you'll probably improve on that as my 150 E-TEC does 1.15nm/L in the cruise (2.1km/L) and I would think yours should be better than that.

The E-TEC engine gauges give you a running readout of fuel economy at the current speed, does the instrumentation on your engine offer anything like that? I found it very useful in finding the sweet spot for economy on my boat, which is about 25-27 knots.

I think falcon meant you should work on a 20% reserve over and above what you expect to use but maybe his percent key was broken

So if you worked on a useful range of 100km on a tank + 20km as a reserve that would be sensible, until you get a better feel for the actual consumption which I suspect may be better than that.
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Old 18 November 2012, 05:12   #6
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Thanks for the guidance. I will work on the 100ks and sneak 10 litres in the front hold just in case. Cheers
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Old 18 November 2012, 05:14   #7
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Driven carefully in good conditions I can get 0.7nm/l, this falls to 0.5nm/l if the conditions are rough or I give it the beans. That's on a heavy 6.4m with twin 115s. As already mentioned your setup should return at least 1nm/l or around 2km/l. Only experience will tell, you need to know your own boat. Start off easy & build up your range as your experience grows.
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Old 18 November 2012, 05:49   #8
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Thats good advice,things like Weather-Tide- load,and driveing style wil all have thier effect.
I have to say I have been VERY pleasantly surprised at my new DF 250 Fuel consumption!!
Not done the sums properly,and I was single handed (although started with a quarter of a Ton of fuel!) but on the Last decent trip.. to Lundy did around 145 miles-on just over 160 litres,...not far off my E-tec figures,and that was a 130! VERY happy Bunny
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