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06 April 2012, 14:20
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#1
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Member
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
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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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06 April 2012, 14:24
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#2
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Member
Country: UK - Wales
Town: N Wales Chester
Boat name: Mr Smith
Make: Humber
Length: 6m +
Join Date: Feb 2009
Posts: 5,238
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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.
http://www.rib.net/forum/f8/whats-it...lly-47288.html
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06 April 2012, 16:03
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#3
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Member
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
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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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06 April 2012, 16:34
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#4
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Member
Country: UK - Wales
Make: XS // Delta
Length: 6m +
Engine: 60hp // 2x90hp
Join Date: Feb 2007
Posts: 213
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afaik, the RC 4.8 is rated to 60hp
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06 April 2012, 16:53
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#5
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Member
Country: UK - England
Town: East Kent and Brittany
Boat name: Cameo
Make: Redbay Stormforce
Length: 6m +
Engine: 200hp Suzuki
MMSI: 235067011
Join Date: Aug 2005
Posts: 123
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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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06 April 2012, 16:55
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#6
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Member
Country: UK - Wales
Town: N Wales Chester
Boat name: Mr Smith
Make: Humber
Length: 6m +
Join Date: Feb 2009
Posts: 5,238
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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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06 April 2012, 18:15
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#7
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Member
Country: UK - England
Town: Southampton
Boat name: SMH Rib / War Shot
Make: Ribtec / Scorpion
Length: 4m +
Engine: 100hp Yam/150hp opt
Join Date: Sep 2003
Posts: 2,069
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My only experience of a 4.8 had a 50hp 4 stroke on it. Not enough power.
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06 April 2012, 18:36
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#8
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Member
Country: UK - Scotland
Town: Stornoway
Make: Scorpion 8.1 mk2
Length: 8m +
Engine: Yamaha F300
Join Date: Aug 2006
Posts: 204
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Yamaha's new F70, only 117 kgs
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06 April 2012, 18:43
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#9
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Member
Country: UK - Wales
Make: XS // Delta
Length: 6m +
Engine: 60hp // 2x90hp
Join Date: Feb 2007
Posts: 213
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Quote:
Originally Posted by Searider
My only experience of a 4.8 had a 50hp 4 stroke on it. Not enough power.
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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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06 April 2012, 18:50
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#10
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Member
Country: UK - England
Town: Bournemouth
Boat name: Seadrive
Make: Capelli Tempest 470
Length: 4m +
Engine: Suzuki DF70
MMSI: 235079113
Join Date: Jul 2008
Posts: 550
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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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06 April 2012, 19:10
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#11
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Member
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
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hi,
thanks for all the replies. Appreciate the point about cost of fuel versus initial outlay. however, I think the time has come to start looking in earnst for a suitable modern replacement--wanting to be kind to the sea/environment and all that. Soumds like I'm looking at either a 60 or 70hp 2/4st. I hadn't really considered YAM as a friend had mentioned all the parts were very pricey. that said, I'll do some digging on the internet and see which specification/model ticks all the boxes, if there is such a thing!
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06 April 2012, 19:12
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#12
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Member
Country: UK - England
Town: South Yorks
Boat name: Black Pig
Make: Ribcraft
Length: 5m +
Engine: DF140a
MMSI: 235111389
Join Date: Feb 2008
Posts: 12,160
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A 75 Etec will sit nicely on there. Sips fuel &oil, light, powerful & 3 year/300hr servicing, works out at less than £100/year.
__________________
Rule#2: Never argue with an idiot. He'll drag you down to his level & then beat you with experience.
Rule#3: Tha' can't educate pork.
Rule#4: Don't feed the troll
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06 April 2012, 19:35
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#13
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Member
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
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Any advantages of the 75 over the 60, apart from the obvious of a little more power, but that is somewhat set off against the just from 138 to 113kg??
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06 April 2012, 20:20
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#14
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Member
Country: UK - England
Town: Ashton-under-Lyne Lancs
Boat name: IMOGEN
Make: Air-Craft 5.4
Length: 5m +
Engine: Suzuki df70a
MMSI: 235087492
Join Date: May 2010
Posts: 7,078
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I have a 60 Etec on my 5.4 Air-Craft and it's great on fuel and I average 31 knots, top speed 34 knots the difference between the two is the 75 is three cylinders as opposed to two and only £500 difference. Your call
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06 April 2012, 22:36
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#15
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Member
Country: UK - Wales
Town: N Wales Chester
Boat name: Mr Smith
Make: Humber
Length: 6m +
Join Date: Feb 2009
Posts: 5,238
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What's the weight difference captain?
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06 April 2012, 22:51
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#16
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Member
Country: UK - England
Town: Ashton-under-Lyne Lancs
Boat name: IMOGEN
Make: Air-Craft 5.4
Length: 5m +
Engine: Suzuki df70a
MMSI: 235087492
Join Date: May 2010
Posts: 7,078
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Quote:
Originally Posted by HUMBER P4VWL
What's the weight difference captain?
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Etec 60 109kg Etec 75 145kg
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06 April 2012, 23:42
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#17
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Member
Country: UK - England
Town: Hull
Make: Bombard
Length: 5m +
Engine: Yam 60 2st
Join Date: Nov 2011
Posts: 195
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Quote:
Originally Posted by physdemon
Any advantages of the 75 over the 60, apart from the obvious of a little more power, but that is somewhat set off against the just from 138 to 113kg??
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I have the Yamaha 60 2st on my 5m Bombard and it goes really well but only weighs about 106Kg 2003 model and 3Cyl. The few long runs I've done show it to be probably more economical than I expected at approx 0.6Lt at 25knots. I doubt you would realy notice any difference if you got a 70 as these add nearly 40kg of weight for the extra little power although the new Yamaha 70 is light too as already mentioned.
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07 April 2012, 00:28
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#18
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Member
Country: UK - Scotland
Boat name: Wildheart
Make: Humber/Delta Seasafe
Length: 5m +
Engine: Merc 60 Clamshell
MMSI: 235068449
Join Date: Apr 2007
Posts: 4,671
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Couple of Jura fueled thoughts- if your boat is full of dive gear, is that weight difference going to be proportionally significantly different? If it is, Clamshells only weigh 85kg.....
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07 April 2012, 01:21
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#19
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Member
Country: UK - Wales
Town: West Wales
Make: Vipermax 5.8, SR4.7
Length: 5m +
Engine: 150 Opti, F50EFi
Join Date: Sep 2005
Posts: 6,299
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Quote:
Originally Posted by IndyR1
I have the Yamaha 60 2st on my 5m Bombard and it goes really well but only weighs about 106Kg 2003 model and 3Cyl. The few long runs I've done show it to be probably more economical than I expected at approx 0.6Lt at 25knots. I doubt you would realy notice any difference if you got a 70 as these add nearly 40kg of weight for the extra little power although the new Yamaha 70 is light too as already mentioned.
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Yam 60 & 70 2-strokes are the same motor. The 75 is bigger (& heavier), same as the 90.
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07 April 2012, 15:38
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#20
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Member
Country: UK - England
Town: South Yorks
Boat name: Black Pig
Make: Ribcraft
Length: 5m +
Engine: DF140a
MMSI: 235111389
Join Date: Feb 2008
Posts: 12,160
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Quote:
Originally Posted by physdemon
Any advantages of the 75 over the 60, apart from the obvious of a little more power, but that is somewhat set off against the just from 138 to 113kg??
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As already said, the 75 is a 3 cyl against the 2 of the 60. The 75 is well regarded & considered a "strong" engine pushing out well over its 75hp rating. The extra cylinder gives more torque than the modest 15hp increase suggests. AND it's a 2 stroke
__________________
Rule#2: Never argue with an idiot. He'll drag you down to his level & then beat you with experience.
Rule#3: Tha' can't educate pork.
Rule#4: Don't feed the troll
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