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Old 23 September 2015, 14:58   #11
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Country: UK - Channel Islands
Town: A large rock
Boat name: La Frette
Make: Osprey Vipermax
Length: 6m +
Engine: 200 Suzzy
Join Date: May 2004
Posts: 2,833
From my fairly restricted experience of shaft drive semi-displacement boats I think shaft speed tends to be around 1750rpm for best efficiency. I guess after that you start to induce too much prop slip and lose thrust. I wonder whether a smaller diameter 4 blade might help. It could be mounted a tad lower which would also keep it further from the surface and reduce ventilation. There is a rule of thumb somewhere about distance between top of prop and underside of hull. I'll let you know if I find it.
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Old 23 September 2015, 16:18   #12
Country: UK - England
Town: Southampton
Make: Ballistic
Length: 7m +
Engine: Yam 225
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Go the clarkson route and fit a oversized OB

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Old 23 September 2015, 16:29   #13
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Country: Ireland
Make: Redbay Boats
Length: 9m +
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All grist for the mill, guys - keep it coming!

"Who knows what evil lurks in the hearts of men?"
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