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Old 16 February 2015, 20:29   #11
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Country: Hong Kong
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Boat name: Skandia 2
Make: Gemini 550
Length: 4m +
Engine: Yamaha FT60
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The link of the "guy" was : Rigid Inflatable Boats (RIB) - Real World Experience | eBay. To be fair he did say " about 14mpg"
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Old 17 February 2015, 09:55   #12
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Country: UK - England
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The oft-quoted rule of thumb on here seems to be about 1 litre per nautical mile, which is about 4.4 statute miles per US gallon.

Matth suggested 0.6 L/nmi in the second post — for a similar sized boat with a recent engine. That's 7.3 mpg (statute, US).

I can't believe a figure of 14 mpg (ditto). That's 0.3 L/nmi, which is half what the lowest figures seem to be on here. Of course there will be quite a bit of variation between boats, engines, payload, conditions and people helming, but 7 mpg isn't 'about 14mpg'.

I think he's made a mistake measuring his fuel consumption, or accidentally put a 1 in front of it.

I'd plan for 1 L/nmi, 5 nautical mpg imperial (or 4 nautical mpg US), and then be pleasantly surprised if your consumption is better than that. It's much better that way than planning for 14 (or, being more conservative, 10) and being disappointed somewhere out at sea !
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Old 17 February 2015, 10:29   #13
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Country: UK - England
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I think to get better than 0.5 litres per nautical mile you would need either a sub 10hp outboard (they just sip fuel) or a diesel inboard.
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Old 17 February 2015, 11:39   #14
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Country: UK - England
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I managed in 2013 to do a shade over 82nm on 32L of fuel .

It was a mirror calm day and I trimmed the boat as well as I could and did 22knts the entire way around the IOW having left Poole.

That's with flat (ish) v on my little Avon adventure 4m and a Yam 50EFI purring along behind me ....only coming of the plane twice the entire way.

What's that work out to ? - About 0.39l per NM ?

Got to love EFI
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Old 18 February 2015, 01:24   #15
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Country: Hong Kong
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Very Good numbers Peter!

There is hope and perhaps credibility to the 14mpg(US) claim. I have the Yam 60 with EFI. Hope to be doing sea trials next week. My Gemini 550 might be a shade heavier at around 300kg for the hull and 120kg for the engine plus extras.

What was your approx displacement at the time and the bottom was antifouled?
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Old 18 February 2015, 03:06   #16
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Country: UK - England
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14 mpg (US gallons) works out at approx 0.30 litres per nautical mile.
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