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Old 01 May 2006, 17:08   #1
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Engine size for rib

hi
Have Narwall 4 metre Rib,what is the largest safe engine I can use.have been running a 40 hp Idears and advice most welcome
stul
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Old 01 May 2006, 17:15   #2
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if boat was made since the recreational craft directive (1994?) then it should have a plate on the transom stating maximum weight and engine size

Below is an extract from a recent MAIB investigation - which shows the recommended safe power. Multiply the answer in kW by 1.341 to get HP.

But if this is bigger than the manufacturers rating it will cause you insurance issues.
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Old 01 May 2006, 18:58   #3
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Quote:
Originally Posted by stul
hi
Have Narwall 4 metre Rib,what is the largest safe engine I can use.have been running a 40 hp Idears and advice most welcome
stul
I have a Narwhal NK400R and the label on the toobs states that the maximum o/board power is 50 hp with a max transom weight of 100 kg

HTH

Andrew
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Old 02 May 2006, 18:39   #4
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Quote:
Originally Posted by Polwart
if boat was made since the recreational craft directive (1994?) then it should have a plate on the transom stating maximum weight and engine size

Below is an extract from a recent MAIB investigation - which shows the recommended safe power. Multiply the answer in kW by 1.341 to get HP.

But if this is bigger than the manufacturers rating it will cause you insurance issues.
Thanks
for info will have to work it out,engine date is 1990,hard to read info on tubes
thanks Stul
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Old 02 May 2006, 18:49   #5
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Quote:
Originally Posted by AndrewH
I have a Narwhal NK400R and the label on the toobs states that the maximum o/board power is 50 hp with a max transom weight of 100 kg

HTH

Andrew
Hi Andy
Hard to read info on toobs or tubes,50 engine max would go well with that,how old is your Narwhal,ps my engine is mounted about 3inches off centre to startboard side is your mounted in the centre?thanks for interest
Stul
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Old 02 May 2006, 20:12   #6
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Hi Andy
How old is your Narwhal
Stul
Can't be sure but I believe about 1996/1997

Quote:
Originally Posted by stul
Hi Andy
ps my engine is mounted about 3inches off centre to startboard side is your mounted in the centre?thanks for interest
Stul
- Bizarre - Mine is slap bang in the middle of the transom. I wonder if any one else here could shed light on that?
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Old 03 May 2006, 07:50   #7
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Quote:
Originally Posted by AndrewH
Can't be sure but I believe about 1996/1997



- Bizarre - Mine is slap bang in the middle of the transom. I wonder if any one else here could shed light on that?
Andy
had a bit of advice about this off a guy called Fast Fred,from usa,see "Fitting A engine" queston below
thanks Stul
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Old 04 May 2006, 08:39   #8
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you can very easily calculate the max engine size off your boat using the current CE marking regulations.

Max engine size i HP = (Lenght * Width * 10 - 33) * 1,341

Length is the max length off the boat without engine
Width is the max outside width off your both.

This is the current CE regulations, so if your boat is CE marked this is the rules that apply to your boat

Best Regards
Rene
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Old 04 May 2006, 08:46   #9
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I see it doesn't take into effect actual hull surface area - how deep the V is etc etc - who came up with this?
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Old 04 May 2006, 08:49   #10
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Codprawn, has a point, my old 4m shallow v Avon was downright dangerous on its maximum 40HP, had to back right off to be able to turn at any great speed or it went sideways. However a 4m Avon Searider deep v will take a 50-60hp no problem.
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