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Old 02 May 2011, 23:26   #1
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Country: UK - England
Town: reading&st.davids.
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Make: osprey eagle 5.6
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Which prop do i need?

I have an osprey eagle 5.6mtr with a 90hp yamaha from about 1996 or thereabouts.It has a piranha plastic prop on it that has seen better days.I think it's around a 13 inch but don't know what pitch.I'd like to replace it with a new aluminium one so can anyone help me with the right size and pitch to use.I am refurbishing the boat and will be using it for cruising with about 2 or 3 people plus fuel for day trips on the solent and other places along the southcoast.
Many thanks,Chris
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Old 03 May 2011, 12:38   #2
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Country: UK - England
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A rough guide is below

PROP SPEEDS

Take max revs and devise by gear ratio, multiply by pitch of prop then devise by 1056

Deduct 10% for slip

That gives theoretical top speed (MPH) before other factors like load, conditions etc are accounted for

Simples

You can use that along with your ideas on your required speed etc to get the right prop.

Hope it helps

Peter ~ askboatsandoutboards4sale@sky.com ~ 07930 421007
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Old 03 May 2011, 14:21   #3
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Country: UK - England
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A good start would be a 17" K series prop.
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Old 06 May 2011, 03:51   #4
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suzuki 90 4 stroke on a 6m rib currently running a 21inch pitch, was previously running a 19 and overrevving.
My merc 90 4 stroke on a 5.5m rib was running a 19 (from memory?). A few replies from folk in the same boat and power area may help you make a decision.
Or ask steel developments for advice via their website before you buy.
Bin the pirahana ( or put it in the bottom of the boat for the day you really need sommat no matter how s**** it is!
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Old 08 May 2011, 16:12   #5
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Quote:
A few replies from folk in the same boat and power area may help you
or perhaps not
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