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13 November 2015, 12:22
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#1
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Member
Country: UK - England
Town: Cambridge
Boat name: SIBylle
Make: Honda Honwave
Length: 3m +
Engine: Honda BF20
MMSI: 235915576
Join Date: Oct 2015
Posts: 431
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Difference in engines
Hi,
I read a post or two talking about the difference in 20HP engines... it seemed to focus on which had more power (can't find post now)... now forgive me if I'm wrong but doesn't 20Hp mean 20Hp so they're all the same? Yam/Honda/Merc/Suzuc/Twat/etc...
I get that 2-stroke will be lighter/lay down the power different to a 4-stroke, and that perhaps EFI will again be a bit different to carb...
But really, is there ANY difference in what these engines can do to propel your 4m SIB forward?
Thanks
Stig
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13 November 2015, 15:20
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#2
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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: 12,178
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Hmm! A couple of things to consider. The ICOMIA standards by which engines are rated allows for a +/-10% variance from what it says on the cowl. So a 20hp engine could be 18-22hp in reality & at these low HPs, 4 is a lot. It could make the difference in running the next pitch prop up or down. The standards are from the old carbed engine days when it was virtually impossible to produce an engine with an exact HP output. The advent of DI/EFI & Engine Management has changed this, hence we now have "HO" engines in the BRP line up, as they are tuned or "Mapped" to the top end of the allowed HP range. If you take the 75hp Etec as an example, this has a reputation for being a "strong" engine & punching above its weight, in theory it could be outputting 82.5hp. The 90hp on the other hand is known to be a tad "Flabby". In theory, the 90hp might only be delivering 81hp. A cynical chap, might argue that the 75&90hp engines are one & the same, but with different cowl stickers & a £500 price difference
The other thing to consider is torque, 2strokes tend to be "Torquier" than 4 strokes, i.e the power is delivered lower down the rev range & with more grunt. Without wanting to re-ignite the whole 2s v 4s argument, in my experience, 2s are faster off the mark that 4strokes due to the low down oomph!
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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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13 November 2015, 18:31
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#3
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Member
Country: UK - England
Town: Wild West
Boat name: No Boat
Make: No Boat
Length: under 3m
Join Date: Jan 2008
Posts: 5,306
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Quote:
Originally Posted by Pikey Dave
Hmm! A couple of things to consider. The ICOMIA standards by which engines are rated allows for a +/-10% variance from what it says on the cowl. So a 20hp engine could be 18-22hp in reality & at these low HPs, 4 is a lot. It could make the difference in running the next pitch prop up or down. The standards are from the old carbed engine days when it was virtually impossible to produce an engine with an exact HP output. The advent of DI/EFI & Engine Management has changed this, hence we now have "HO" engines in the BRP line up, as they are tuned or "Mapped" to the top end of the allowed HP range. If you take the 75hp Etec as an example, this has a reputation for being a "strong" engine & punching above its weight, in theory it could be outputting 82.5hp. The 90hp on the other hand is known to be a tad "Flabby". In theory, the 90hp might only be delivering 81hp. A cynical chap, might argue that the 75&90hp engines are one & the same, but with different cowl stickers & a £500 price difference
The other thing to consider is torque, 2strokes tend to be "Torquier" than 4 strokes, i.e the power is delivered lower down the rev range & with more grunt. Without wanting to re-ignite the whole 2s v 4s argument, in my experience, 2s are faster off the mark that 4strokes due to the low down oomph!
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The main thing in my experience your after in any RIB is Hole shot and grip...last year Chris and I did a Hole shot...short drag test with my 250 Suz...low hours against his..a new 25O e-tec...(Both Boats propped perfectly) which he filmed.
Boats more or less same size ...although mine is a bit heavier. A Real world test flat water...(St Martins Harbour)
result...NOTHING in it at all!
So ( at least with the the Big uns)...you may want to re-think that one Dave
By the way Top end would be within a knot or two as well.
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A clever Man learns by his mistakes..
A Wise Man learns by other people's!
The Road to HELL ..is Paved with "Good inventions!"
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13 November 2015, 19:06
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#4
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Member
Country: UK - England
Town: Retford
Boat name: Spy-sea-one
Make: Excel 435
Length: 4m +
Engine: Suzuki Outboard/25/4
Join Date: Oct 2011
Posts: 7,532
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IMO there are so many variables on the finished installation engine to boat that I go for largest hp the boat can take unless budget prevents, the reason I like redundancy, because how you use it today can be totally different tomorrow, in my diving days weight was crucial 4 m boat 25hp engine 2 divers plus kit and a boat man on the plane ok, 3 divers and kit not a hope in hell, we even use to start the aux to get it on the plane.my take is 5hp is a lot when you need it so when buying get more power than you need cost goes up of course 20 to a 25 but if it doesn't perform changing to a 25 later costs more.i agree with both Dave & max Dave's theory and Max's trial if Dave is right would two engines perform exactly the same which would affect Max's trial if they didn't ?
Cheers
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13 November 2015, 19:47
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#5
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Member
Country: UK - England
Town: Bristol
Make: Ribcraft
Length: 5m +
Engine: Yamaha
Join Date: May 2006
Posts: 4,299
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Quote:
Originally Posted by Maximus
The main thing in my experience your after in any RIB is Hole shot and grip...last year Chris and I did a Hole shot...short drag test with my 250 Suz...low hours against his..a new 25O e-tec...(Both Boats propped perfectly) which he filmed.
Boats more or less same size ...although mine is a bit heavier. A Real world test flat water...(St Martins Harbour)
result...NOTHING in it at all!
So ( at least with the the Big uns)...you may want to re-think that one Dave
By the way Top end would be within a knot or two as well.
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Hmm I would put the RC at a much heavier build than the other. so what your saying is that there was nothing in it?
With this accurate info to hand ,this kinda dilutes the necessity to run a two stroke(with very expensive oil) at all if performance is mirroring or less than a four stroke AND with a much heavier boat.
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Member of S.A.B.S. West Country Division
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13 November 2015, 19:49
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#6
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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: 12,178
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Quote:
Originally Posted by Maximus
So ( at least with the the Big uns)...you may want to re-think that one Dave
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Aye! 'appen Chris had a full tank of fuel
__________________
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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13 November 2015, 19:54
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#7
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Member
Country: UK - England
Town: Bristol
Make: Ribcraft
Length: 5m +
Engine: Yamaha
Join Date: May 2006
Posts: 4,299
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I wonder who got back to the mainland first? the Etic or the Suzook?
Gonna put me money on the Suzuki!
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Member of S.A.B.S. West Country Division
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13 November 2015, 19:55
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#8
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Member
Country: UK - England
Town: Wakefield
Boat name: Bouncer
Make: Redbay Stormforce
Length: 6m +
Engine: 2x Honda 100 Hp
MMSI: 235025718
Join Date: Jun 2009
Posts: 4,177
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Quote:
Originally Posted by Pikey Dave
Aye! 'appen Chris had a full tank of fuel
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Oooh🙈🙈
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13 November 2015, 20:01
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#9
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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: 12,178
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Quote:
Originally Posted by matt h
Gonna put me money on the Suzuki!
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Double or quits?
__________________
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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13 November 2015, 20:04
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#10
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Member
Country: UK - England
Town: Bristol
Make: Ribcraft
Length: 5m +
Engine: Yamaha
Join Date: May 2006
Posts: 4,299
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Double ha ha and a used tin of WD 40
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Member of S.A.B.S. West Country Division
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13 November 2015, 20:11
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#11
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Member
Country: UK - England
Town: Wild West
Boat name: No Boat
Make: No Boat
Length: under 3m
Join Date: Jan 2008
Posts: 5,306
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Quote:
Originally Posted by Pikey Dave
Aye! 'appen Chris had a full tank of fuel
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Funny that....we'd both just re-fuelled at the Quay as I remember.
Maybe the jump from twins to a single has squewed your thinking??....I'll look forward to you finally having a go in mine next time we're out....
IF...you can handle going over 20 knts!
__________________
A clever Man learns by his mistakes..
A Wise Man learns by other people's!
The Road to HELL ..is Paved with "Good inventions!"
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13 November 2015, 20:15
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#12
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Member
Country: UK - England
Town: Bristol
Make: Ribcraft
Length: 5m +
Engine: Yamaha
Join Date: May 2006
Posts: 4,299
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Ah. so who got back to the mainland first (as a race was compulsary and inevitable)and how far was the 4 stroke ahead in the end?
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Member of S.A.B.S. West Country Division
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13 November 2015, 20:25
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#13
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RIBnet admin team
Country: Ireland
Length: 4m +
Join Date: Feb 2008
Posts: 14,910
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__________________
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13 November 2015, 22:09
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#14
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RIBnet admin team
Country: UK - Scotland
Boat name: imposter
Make: FunYak
Length: 3m +
Engine: Tohatsu 30HP
MMSI: 235089819
Join Date: Sep 2005
Posts: 11,632
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Quote:
Originally Posted by Maximus
By the way Top end would be within a knot or two as well.
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So he was two knots faster than you then ;-)
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14 November 2015, 09:30
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#15
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RIBnet supporter
Country: UK - England
Town: Warwickshire
Boat name: Impulse
Make: Ribcraft
Length: 5m +
Engine: Suzuki 140
Join Date: Sep 2011
Posts: 1,020
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I have driven Maxi's boat although it is a heavy boat as Ribcraft don't skimp on the build it is a very capable and very fast boat. Come on you two who won don't keep us in suspense?????
Sent from my iPhone using RIB Net
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14 November 2015, 10:23
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#16
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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: 12,178
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Quote:
Originally Posted by Maximus
IF...you can handle going over 20 knts!
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Oh I dunno about that. I read somewhere on 'tinternet that if you go above 20kn your head can explode & your balls drop off.
I'll stick to being the tortoise to your hare if you don't mind😄
.....sh1t happens.......
__________________
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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