Reply
 
Thread Tools Search this Thread
 
Old 06 April 2012, 14:20   #1
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
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.
__________________
physdemon is offline   Reply With Quote
Old 06 April 2012, 14:24   #2
Member
 
HUMBER P4VWL's Avatar
 
Country: UK - Wales
Town: N Wales Chester
Boat name: Mr Smith
Make: Humber
Length: 6m +
Join Date: Feb 2009
Posts: 5,238
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
__________________
HUMBER P4VWL is offline   Reply With Quote
Old 06 April 2012, 16:03   #3
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
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.
__________________
physdemon is offline   Reply With Quote
Old 06 April 2012, 16:34   #4
Member
 
TonyC's Avatar
 
Country: UK - Wales
Make: XS // Delta
Length: 6m +
Engine: 60hp // 2x90hp
Join Date: Feb 2007
Posts: 213
afaik, the RC 4.8 is rated to 60hp
__________________
TonyC is offline   Reply With Quote
Old 06 April 2012, 16:53   #5
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
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.
__________________
horacebat is offline   Reply With Quote
Old 06 April 2012, 16:55   #6
Member
 
HUMBER P4VWL's Avatar
 
Country: UK - Wales
Town: N Wales Chester
Boat name: Mr Smith
Make: Humber
Length: 6m +
Join Date: Feb 2009
Posts: 5,238
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.
__________________
HUMBER P4VWL is offline   Reply With Quote
Old 06 April 2012, 18:15   #7
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
RIBase
My only experience of a 4.8 had a 50hp 4 stroke on it. Not enough power.
__________________
Searider is offline   Reply With Quote
Old 06 April 2012, 18:36   #8
Member
 
Country: UK - Scotland
Town: Stornoway
Make: Scorpion 8.1 mk2
Length: 8m +
Engine: Yamaha F300
Join Date: Aug 2006
Posts: 204
Yamaha's new F70, only 117 kgs
Attached Thumbnails
Click image for larger version

Name:	phpThumb_generated_thumbnailjpg.jpg
Views:	286
Size:	25.5 KB
ID:	66891  
__________________
Robbie Diesel is offline   Reply With Quote
Old 06 April 2012, 18:43   #9
Member
 
TonyC's Avatar
 
Country: UK - Wales
Make: XS // Delta
Length: 6m +
Engine: 60hp // 2x90hp
Join Date: Feb 2007
Posts: 213
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.
__________________
TonyC is offline   Reply With Quote
Old 06 April 2012, 18:50   #10
Member
 
longjohn's Avatar
 
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
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!
__________________
longjohn is offline   Reply With Quote
Old 06 April 2012, 19:10   #11
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
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!
__________________
physdemon is offline   Reply With Quote
Old 06 April 2012, 19:12   #12
Member
 
Pikey Dave's Avatar
 
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
RIBase
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
Pikey Dave is offline   Reply With Quote
Old 06 April 2012, 19:35   #13
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
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??
__________________
physdemon is offline   Reply With Quote
Old 06 April 2012, 20:20   #14
Member
 
kerny's Avatar
 
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
RIBase
Send a message via Skype™ to kerny
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
__________________
kerny is offline   Reply With Quote
Old 06 April 2012, 22:36   #15
Member
 
HUMBER P4VWL's Avatar
 
Country: UK - Wales
Town: N Wales Chester
Boat name: Mr Smith
Make: Humber
Length: 6m +
Join Date: Feb 2009
Posts: 5,238
What's the weight difference captain?
__________________
HUMBER P4VWL is offline   Reply With Quote
Old 06 April 2012, 22:51   #16
Member
 
kerny's Avatar
 
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
RIBase
Send a message via Skype™ to kerny
Quote:
Originally Posted by HUMBER P4VWL View Post
What's the weight difference captain?
Etec 60 109kg Etec 75 145kg
__________________
kerny is offline   Reply With Quote
Old 06 April 2012, 23:42   #17
Member
 
IndyR1's Avatar
 
Country: UK - England
Town: Hull
Make: Bombard
Length: 5m +
Engine: Yam 60 2st
Join Date: Nov 2011
Posts: 195
Quote:
Originally Posted by physdemon View Post
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??
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.
__________________
Si
IndyR1 is offline   Reply With Quote
Old 07 April 2012, 00:28   #18
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
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.....
__________________
9D280 is offline   Reply With Quote
Old 07 April 2012, 01:21   #19
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
Quote:
Originally Posted by IndyR1 View Post
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.
Yam 60 & 70 2-strokes are the same motor. The 75 is bigger (& heavier), same as the 90.
__________________
Downhilldai is offline   Reply With Quote
Old 07 April 2012, 15:38   #20
Member
 
Pikey Dave's Avatar
 
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
RIBase
Quote:
Originally Posted by physdemon View Post
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??
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
Pikey Dave is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off




All times are GMT. The time now is 01:24.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2024, vBulletin Solutions, Inc.