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Old 06 April 2012, 09:20   #1
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Country: UK - England
Town: newcastle upo tyne
Boat name: vyper1
Make: Ribcraft 4.8
Length: 4m +
Engine: outboard, petrol, 75
Join Date: Jul 2010
Posts: 25
Repowering 4.8m Ribcraft

Hi,

Just wondering if anyone has any strong thoughts on what engine would suit my 4.8m ribcraft. Currently powered by a 75hp 1999 Mercury 2 st, but seems a little heavy on fuel compared to my old boat--5.8m tornado, powered by 115hp 2 st. Two obvious choices are the etec's and TLDI's. I use the boat mainly for diving with one coax and two divers plus kit. The 75hp pushes the boat along well, but seems to gulp the fuel off no matter how much I open the throttle--currently using 20-25mph as the baseline for cuising speed. Top speed is around 35mph. Over the last season I have been considering whether now is the time to repower, realising the best price for the carburettor engine, and opting for a fuel injection model, and thereby hopefully realising better fuel economy. Given my intended use, size of the boat, and current experiences of older v newer type engines, I'm looking for some advice on engine size and type from those more in the know. All advice/comments welcome from you seasonned ribbers.
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Old 06 April 2012, 09:24   #2
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Country: UK - Wales
Town: N Wales Chester
Boat name: Mr Smith
Make: Humber
Length: 6m +
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Your limit may be 75, but what's the weight limit?

Check, then check this!!! The opti will use just over half the fuel than a carbed 2s. We moved from 75 carb to 90 opti, worlds apart.

This below is a bargain.

Whats it worth?(Realistically)
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Old 06 April 2012, 11:03   #3
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Country: UK - England
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Boat name: vyper1
Make: Ribcraft 4.8
Length: 4m +
Engine: outboard, petrol, 75
Join Date: Jul 2010
Posts: 25
Hi,

thanks for the reply. Just had a quick look at Mercury's page re: the optimax 75: can't quite understand why the entire range has a weight of 170kg; seems a heavy engine to me. looked on line and the existing engine is weighing in around 138kg; so looking to repower with something around this weight or lighter. the newer 75's all look a shade above this tldi and etec type. Might then need to start looking for 60hp mariner 4 st or 60hp etec; the 50hp tldi might then be a bit light on cc's considering. Any thoughts from anyone, again, welcome.
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Old 06 April 2012, 11:34   #4
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Country: UK - Wales
Make: XS // Delta
Length: 6m +
Engine: 60hp // 2x90hp
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afaik, the RC 4.8 is rated to 60hp
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Old 06 April 2012, 11:53   #5
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Country: UK - England
Town: London, Kent and Brittany
Boat name: Cameo
Make: Redbay Stormforce
Length: 6m +
Engine: 200hp Suzuki
MMSI: 235067011
Join Date: Aug 2005
Posts: 101
I've got a 60hp 2st Mariner on mine, but according to the owners manual that they kindly sent through earlier in the year the 4.8 maximum is 56kw / 75hp.
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Old 06 April 2012, 11:55   #6
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The 75,90,115 and 125 hp are all the same block. A 1.5L 3cyl. Hence other engines that cover the 40-70 range are generally a smaller block, hence lighter. But that engine could be a steal.
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Old 06 April 2012, 13:15   #7
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Country: UK - England
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Boat name: SMH Rib / War Shot
Make: Ribtec / Scorpion
Length: 4m +
Engine: 10hp Yam / 150hp opt
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RIBase
My only experience of a 4.8 had a 50hp 4 stroke on it. Not enough power.
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Old 06 April 2012, 13:36   #8
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Country: UK - Scotland
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Yamaha's new F70, only 117 kgs
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Old 06 April 2012, 13:43   #9
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Quote:
Originally Posted by Searider View Post
My only experience of a 4.8 had a 50hp 4 stroke on it. Not enough power.
Your kidding right? The Club has 4 x 4.8's, all with Suzuki 50's on them and they are like shit off a shovel.
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Old 06 April 2012, 13:50   #10
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Country: UK - England
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Boat name: Seadrive
Make: Capelli Tempest 470
Length: 4m +
Engine: Suzuki DF70
MMSI: 235079113
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Posts: 540
You can buy a lot of fuel for the price of a new motor - so the payback is going to be a long time or maybe never!
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