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Old 08 July 2006, 17:15   #1
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Country: UK - England
Town: St Austell
Boat name: Ghostrider
Make: BWM
Length: 7m +
Engine: 260HP inboard diesel
MMSI: 235065724
Join Date: Jul 2006
Posts: 8
Johnson 110 1989 ex racing rib.

Be grateful if somebody knows of an extra long leg for this engine. Have acquired this formula 3 racing rib 'retribution' ( won british nationals 2 years ago). Hull has a 6 inch step in it 16 inches from the stern. It was set up for racing, and I need to get the prop lower in the water for more everyday use. The engine has been lowered right down on to the transom. It can not go any lower.It has a standard 13 x 17 prop on where as before it had a surface piercing prop. from a standing start it takes off fine, but it looses grip from ventilation as the nose comes down. Be grateful for any advice, thoughts ect.
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Old 08 July 2006, 17:46   #2
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Country: UK - Wales
Town: West Wales
Make: Vipermax 5.8, SR4.7
Length: 5m +
Engine: 150 Opti, F50EFi
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Posts: 6,298
Where does the cavitation plate now sit, relative to the level of the underside of the hull, when the engine is trimmed all the way in?
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Old 09 July 2006, 05:58   #3
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Country: UK - England
Town: St Austell
Boat name: Ghostrider
Make: BWM
Length: 7m +
Engine: 260HP inboard diesel
MMSI: 235065724
Join Date: Jul 2006
Posts: 8
ex race rib.

Hi,
The cavitation ( Ventilation) plate is definitely in the wrong place. If you follow a line along the bottom of the hull, ignoring the step, this line is about two thirds to three quarters up the propellor hub's diameter. Have a photo but will have to find out how to put it on the forum. The prop is sucking air in and loosing grip hence I can only think of finding a longer gear casing. Any other thoughts ? Appreciate your help.
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Old 09 July 2006, 12:41   #4
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Country: UK - Wales
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Engine: 150 Opti, F50EFi
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Posts: 6,298
With that set-up, it's definitely going to ventilate.
You'll either have to get a longer leg, as you're planning, or reduce the transom height - is this possible on your boat?
If the engine is a 'long-shaft', you'll need around 21" from the top of the transom to the underside of the hull.
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Old 10 July 2006, 06:52   #5
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Country: UK - England
Town: St Austell
Boat name: Ghostrider
Make: BWM
Length: 7m +
Engine: 260HP inboard diesel
MMSI: 235065724
Join Date: Jul 2006
Posts: 8
I cannot lower the transom any more than it is. My only choice is too either
a)find a 25 inch gearbox ( its a 20 inch on it)
b) find another engine
c) Take the whole lot back to the person that said it would all work fine !!!
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Old 10 July 2006, 07:30   #6
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Country: USA
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Boat name: Miss bad 61
Make: Crapko, AKA Mako
Length: 5m +
Engine: OMC Mod50
Join Date: Apr 2006
Posts: 398
show a pic of it, maybe tranfur some weight, maybe change the style of prop.
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