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Old 13 December 2003, 13:11   #1
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Country: UK - England
Town: isles of scilly
Boat name: Still Miss behavin
Make: Ribcraft
Length: 6m +
Engine: 250 suzuki
Join Date: Dec 2003
Posts: 129
more speed

hi i'm after some info regarding getting more speed out of my rib.
The current set up is a 5.5m delta dash powered by twin suzuki dt 65's with standard 16' pitch 3 blade alloy props set on the lowest height on the transom. Currently i get 36 knots (gps) flat out at 5300rpm on the tachos.
I don't really want to change pitch drastically to get speed at the cost of acceleration But i'm thinking that stainless props would help (anyone know how much) and also been told to raise the engines on the transom by a hole to reduce drag.?
I'm after over 40 knots really so has anyone got any tips advice to get this performance.
thanks in advance
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Old 13 December 2003, 15:05   #2
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Boat name: TOP CAT 2
Make: Scorpion 8.1
Length: 8m +
Engine: 250hp HO
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not a 100% sure but i think if you swap your thick bendy ally prop for an equal stainless item typically people see a gain of 2-3mph. I addes 2 blades kept the same pitch and changed to stainless and didnt loose or gain any speed at all so hopefully its somewhere near right
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Old 13 December 2003, 16:43   #3
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Country: UK - England
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Boat name: April Lass
Make: Moody 31
Length: 9m +
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Posts: 4,850
Blimey I am astonished that you manage to get 36 knots, thats going some. You could change to S/S which would then let you raise the engine a hole but I am not sure the benefit would be worth the cost or trouble. The higher the props the easier they will ventilate everytime you go over a wave and the props come near the surface and with twin engines thats a lot more often than a single.

Big gains in speed require hp and fuel. There was a Delta for sale on Hayling Island with a 150 V6 merc on the back end a few years ago. That would have been very quick (and scary)

Pete
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Old 13 December 2003, 21:41   #4
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Country: Canada
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do lift the engine up. this will decrease the drag and allow more rpms. every boat is differant and only trying will tell. i raised our engines all the way and got 6 knots. did have to buy new props though cause of the rpms. the boat handles better and does not blow out in corners or come of the water over every wave. good luck
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