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Old 20 May 2013, 16:52   #11
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Originally Posted by keith81 View Post
Thanks for the help guys first quote came back at 215 got in touch craft insure they quoted me 70 no brainer I reckon. thanks again.
Well done you
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Old 21 May 2013, 14:24   #12
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How are you supposed to know-there's no data available. If there was, they'd already have it.
you can work out the maximum speed the engine is capable of though:

Max speed = max_rpm x 60 x prop_pitch (inches) / gearbox_ratio x 72913

You will never go faster than that with that engine / prop combo. (And probably only 90% of it).

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Go for 18-20 then, might mean a cheaper quote
Never a good idea to mislead insurers on 'potential risk' though - it gives them an excuse later.
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Old 21 May 2013, 16:41   #13
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Originally Posted by Poly View Post
you can work out the maximum speed the engine is capable of though:

Max speed = max_rpm x 60 x prop_pitch (inches) / gearbox_ratio x 72913

You will never go faster than that with that engine / prop combo. (And probably only 90% of it).



Never a good idea to mislead insurers on 'potential risk' though - it gives them an excuse later.
There has to be a "mass" there somewhere?
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Old 21 May 2013, 16:54   #14
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There has to be a "mass" there somewhere?
No. This is nothing to do with power or acceleration - this is simply how fast a particular prop spinning through water (with zero slip) could propel a boat. The boat could be the QE2 or a carbon fibre canoe - but it will never be able to go faster than the engine can move the prop.
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Old 01 June 2013, 13:08   #15
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Whaaaaa? You lost me at max rpm.... :o)
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