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Old 07 May 2010, 14:50   #1
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2 x 300 hp on a 5.5mtr rib. OH YES !!!!!

Well not really..

I was looking on the net to see if there is a hp to boat size formula .

Building a 5.5 rib home build and thought a 150hp extra long shaft would do the job.
No make of vessel .Splash.

The transom is 60mm Solid well over the top reinforced and what with rear pods and a big knee bracket support's to 20 mm from the top of the transom.

Well over the top specs . weight not known yet as it is still to complete.
fuel tank volume should be around 180 ish ltrs.

so how does one decide on hp for the vessel.
an extra long shaft engine is required due to transom height.
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Old 07 May 2010, 14:55   #2
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Any idea of the weight?

Something around a 115hp should do?
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Old 07 May 2010, 15:05   #3
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this thread might be useful http://rib.net/forum/showthread.php?...hlight=formula
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Old 07 May 2010, 15:06   #4
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Any idea of the weight?

Something around a 115hp should do?
Not yet i am going to have to finish it first before i can weigh it.
but the length should be 5.4 to 5.5.

a little heaver than most I expect due to the layup and hard nose.
along with a higher freeboard of 150.
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Old 08 May 2010, 09:01   #5
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Depends on the weight of the hull but 135 would be about right IMO
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Old 08 May 2010, 09:07   #6
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Very useful many thanks
Robert
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Old 08 May 2010, 14:52   #7
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a 90 opti goes well on a 5.5m lights well balnced great setup
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Old 08 May 2010, 15:08   #8
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a 90 opti goes well on a 5.5m lights well balanced great setup
I had on the last rib I owned twin 50s on a 5.6 and that was 30 knots.
Thinking 150 may push what could be a heavier rib about the same speed.

But due to illness when it's completed i will be able to see how fast it goes.But won't have a go.
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Old 10 May 2010, 08:15   #9
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As a guide for you, the 5.5m Vipermax is rated to 135hp and the 5.5 Northcraft is 150 hp
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Old 10 May 2010, 09:41   #10
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As a guide for you, the 5.5m Vipermax is rated to 135hp and the 5.5 Northcraft is 150 hp
This one is well over the top on construction.
So I am thinking the 150 and see how it goes.
Having said that It's not a vessel I will be going in so it's up to Rob whom owns it what he will put in .

But many thanks for the valuable information.
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