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Old 25 June 2019, 11:29   #1
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Ribcraft 585 / 680 fuel economy cruise/WOT

Hi Everyone,

In the process of finally finalising an order - well sort of

Many thanks to those of you on here who have given advice over PM and email / phone it is very much appreciated

Looking at the Ribcraft website and various threads here it looks like these are typical

585 with 140/150hp c. 0.8-1 l/nm throughout the rev range max 35-40 knots

680 with 200-250hp c.1.2-1.8 l/nm depending very much on revs speed up to just shy of 50 knots

Now I have heard and seen various reports some 680 owners are getting 0.8-1 l/nm but I am trying to get an idea at what cruise and if this is an absolute ideal and if generally its more

Basically trying to get some more info to inform which way ultimately I go

Hope to get to see a couple more 585/680 to get my eye into the overall jump in size as can see the advantages of the bigger size (as mentioned on the other thread going) and the advantages of the smaller size in terms of beaching / towing etc

Nightmare decisions
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Old 25 June 2019, 12:42   #2
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My son has a 6.8 with v6 df200 and at a cruise of about 22-27 mph he gets 0.9l per statute mile.

It will do just over 50mph with his normal loading.

He tows the 6.8 with a grand Cherokee as the 6.8 is the wrong side of 2k for a normal car. He also had to sit the towing test, not sure if a 585 would be any different.

He left the forum quite a while ago but if you need specific info I can ask him?
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Old 25 June 2019, 15:49   #3
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Yes it was your son x59d who posted about just sub 1l/nm for a cruise which is amazing given the extra weight i guess unlike the 585 the fuel consumption goes north exponentially when you hit the loud button. Just trying to get a range of responses
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Old 25 June 2019, 16:15   #4
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I had a 585 with a 140 Suzuki and it replicated the fuel use on the Suzuki website. Whilst I didnít trade up to a ribcraft I have a 6.8 Shearwater Cutter which I rigged with a new 200hp Yamaha. The Shearwater is a heavy build. 585 topped 40knts whilst the 6.8 tops 42knts. Steady cruising in 585 was 20 to 25knts at 0.8 l/m. The 6.8 cruises 25 to 30knts at 1.1l/m. 585 will tow on single axle 6.8 you will probably need twin. Weight of trailer 585 was around 1800kg and 6.8 around 2300kg.
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Old 25 June 2019, 16:15   #5
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Well it stands to reason the louder you push the loud button the more you burn.

The easiest way to look at it is 1 litre per MPH upto about 35mph them it gets up there.
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Old 25 June 2019, 22:39   #6
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Over a season the actual amount you spend on fuel is not that high and differences between boats and engines quite small in total real terms

My advise would buy what suits you and ignore economy as it makes little difference. If you use it 20 times a year you will do well and that will most likely only between £100 and £200 difference in fuel one over the other is that really worth worrying about
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Old 26 June 2019, 05:08   #7
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The difference between 585 and 680 is very real in real terms itís a chunky jump in terms of cash. Do you have either or have bought either from new? Granted on the fuel is they moderately slightly more thirsty on the bigger boat but that is why I am asking for real owners opinions both at cruise and full chat
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Old 26 June 2019, 05:23   #8
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So I've asked him for you and basically cruise is 22-35lph depending on how fast he wants to cruise. If you open it right up you will be close to 70lph with his setup.

Last year a 585 and his 6.8 were side by side and the difference in size is substantial and he priced both so knows the cost difference too.
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Old 26 June 2019, 05:34   #9
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Thanks nocando your posts were helpful as was this was above - my previous post was referring to the gentleman who said there was very little between the boats costs wise obviously there is for build costs I guess at full chat basis 70 lph we are looking at 1.6 - 1.7 l/nm vs 0.9/1 l/nm at cruise. Just need to get some more ideas from other other 585 / 680 owners
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Old 26 June 2019, 16:57   #10
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Hi Rick,

Really don't think you'll get anything like 0.8l/NM for a decent cruising speed in a 6.8. i'd estimate nothing better than 1l/NM - 25%increase in fuel consumption.

my 585 with a 140 $Stroke gives me 0.78l /NM at a comfortable 25kts cruising speed

That's a comfortable speed for size. Can go faster, but burn more fuel for no real benefit, and with harder ride unless flat calm.

A longer hull will enable comfortable cruising a higher speed but at higher fuel burn, and is it just speed you want - what's the benefit of the extra 5kts on a day out?
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