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Old 25 September 2010, 17:22   #11
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Hi and welcome.

I have a 9m Parker (commercial spec, so heavy and well equipped) and run 2x250 Verado's.
I was a 2 stroke addict and reluctant to change to 4 stroke. I have no regrets at all.
The difference in full consumption between engines of a simular size will be insignificant compared to how heavy you are with your right hand! And for 50 hours/year, other costs will have more impact on your pocket.
I can only give you my figures which are when loaded with 10/14 persons and 440ltrs of fuel;-
20kts - 45ltrs/hour ish
25kts - 55-60/hour ish
30kts - 73/hour ish
45kts+ -200/hour!

As for the selection of your boat, go try as many engines as you can and find what you like, we all have attachments to our own preferances.
Steve
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Old 25 September 2010, 17:26   #12
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Thanks to all of you for taking the time to post.
Engine leg seems to be out as it seems they wouldn't allow problem free beaching.
Bigmuz recommend 350hp for a rib designed to handle 600hp. Would that prevent the rib to achieve it's designed performance or require the single to be pushed very hard?
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Old 25 September 2010, 17:57   #13
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Originally Posted by CaptainGb View Post
Bigmuz recommend 350hp for a rib designed to handle 600hp. Would that prevent the rib to achieve it's designed performance or require the single to be pushed very hard?
Just telling it like I see it .. a single 275 Verado pushed my 8.5 like it wasnt there .. you get two of them if you want with all the outboard costs and all the petrol they will drink.. if you have the petrol money in the budget .. stroll on but for all the hours you will be doing .. i think you would be wasting cash .. but ofcourse it depends where you sail ?
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Old 25 September 2010, 18:01   #14
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Good morning all ... my first post on this forum. I'm planning to order a new rib, between 8 and 9 m, for west country cruising and just having fun. Regarding engine setup, what do you think my litres/miles would be for twin 250hp? Is there anything equivalent in term of power using diesel fuel?
The usage will be purely private, maybe 50 hours per year. so do you think petrol O/B will be more cost effective over few years (taking into account purchase cost, maintenance and fuel use)? If O/B, E-Tec or 4 stroke?
Also, can diesel ribs be easily beached? I'm thinking about the drive protection.

Thanks in advance.
Hi there with regards to your questions on fuel consumption that's going depend on a lot of factors not least which hull you are chosing however your probably looking at about 80-100 litres per hour for each engine for the E-tec 250's at full chat and about 40-50 litres each at cruising speed.

50 hours a year is not that much and you will only need to do a few of longer day trips at 8 hours per day and you will soon find yourself clocking up 100 hours.

So if you are looking at average fuel consumption of say 100 litres per hour (assuming time spent at idle etc) then you would use 10000 litres per year so annual fuel costs at current rates will be 12,000

Which Rib are you thinking of getting?

Chris
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Old 25 September 2010, 18:11   #15
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Originally Posted by CaptainGb View Post
Thanks to all of you for taking the time to post.
Engine leg seems to be out as it seems they wouldn't allow problem free beaching.
Bigmuz recommend 350hp for a rib designed to handle 600hp. Would that prevent the rib to achieve it's designed performance or require the single to be pushed very hard?
What are you planning to use it for? Most people here are quite enthusiastic about power/speed - but I doubt many would feel the need for 500 HP on the back of an 8m boat if its just for general leisure / family use. Also twin engines are generally considered inefficient, so e.g. 2x250 HP is possibly equivalent to 1x350 (30% loss?).
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Old 25 September 2010, 18:12   #16
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Ah now ! that's another kettle of worms, the old big single or medium twins question. IMO (don't forget opinions are like ar***es, everybodies got one) depending on how deep your pockets are I'd go down the twin route & put at least 500hp on the back. If its rated at 600hp, then it will probably need 450 to perform. There's NOTHING worse than an underpowered boat, hp is like money & sex, you can't have too much of either. Flogging an underpowered boat will use more fuel, than running a comfortably powered one at it's most efficient rpm. Remember when it comes to engines 1+1 doesn't =2, more like 1.5
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Old 25 September 2010, 18:25   #17
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Well, the one rib I find interesting is the ribcraft 850 cruiser. To be based in the Falmouth area and used for local fun days out and longer ones to the scillies.
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Old 25 September 2010, 18:36   #18
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Well, the one rib I find interesting is the ribcraft 850 cruiser. To be based in the Falmouth area and used for local fun days out and longer ones to the scillies.
& what is pushing it?
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Old 26 September 2010, 03:04   #19
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I have a yamaha 200 2 stroke pushing a 7.5m cobra rib, top speed about 46knots, don't know about litres per hour but a full day out cruising along coast stopping for lunch andnhaving a few bursts of speed I probably get through about 70 quids worth.
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Old 26 September 2010, 05:51   #20
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Well, the one rib I find interesting is the ribcraft 850 cruiser. To be based in the Falmouth area and used for local fun days out and longer ones to the scillies.
Why have you narrowed your choice down to that boat? Do you really need 8.5m for what you suggest? especially if you are only using it 50 hrs a year which suggests "nice weather" rather than must go out every week regardless.

On the 2009 IoM trip (which didn't go because of the weather) I had the pleasure to be a passenger on a 7.8m Ribcraft with single 250 HP (Yam) - in some rather lively conditions. The boat was more than capable (hardy soles with smaller boats ventured out too and survived). I'm quite sure the boat would have made it to the IoM too with the very capable Mr Kennet at the helm - but it wouldn't have been fun - but even an extra 70cm wouldn't have sorted that.

I wouldn't have said it was undepowered either - unless you have a hidden desire to get into racing - it was still getting air borne.

Mollers cruises in the sort of area you are in and likes his trips to the Sillies - which he seems to manage in an Osprey about 2m shorter than you are looking at.

So unless you've got money burning a hole in your pocket, a desire to pay more for fuel, pay more to store it, a bigger status symbol, or a massive family etc... then I'd suggest you try some of the shorter boats - you might be pleasantly surprised.

EDIT: Oh, and I'm not sure I'd be wanting to beach an 8.5m, 60000+ rib regularly either
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