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Old 12 September 2008, 11:46   #11
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Quote:
Originally Posted by Simon B View Post
The number of blades relate to the props ability to transmit "torque" for the same pitch (distance travelled)
Also means the engine can't turn it as fast if you have more blades.
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Old 12 September 2008, 14:11   #12
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This would manifest itself as the engine needing more torque to turn it at the same rpm, the engine may indeed have this torque so you would not notice it, however, if your first prop was correct for WOT then a prop with more blades may reduce your WOT.
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Old 12 September 2008, 14:54   #13
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K.. ta boys I think Andy has a point too with the 'black art' comment, as with some of the new 4 strokes, the power band seems different ?. So some of the traditional rules perhaps are somewhat diluted now. The Honda hub is interchangeable with the merc, so that opens up the range a bit.
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Old 14 September 2008, 16:51   #14
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can only comment on my own experiance:

had a twin delta with dt 65's and changed from the standard suzuki alloy props which were i seem to remember 16" pitch to two solas stainless props sent from steel development as a direct replacement.
The engines overrevved massively 6200 at wot compared to 5800 on the alloys (measured on rpm gauges) so i sent them back and they cupped them up a bit.
They were then at the top of the rev range when trimmed right out but were ok because as steel dev' said once you have small weed growth or are loaded then they will perform.

I found the top end only 2-3 knots higher on SS and also the standing start was simular...however the mid range punch was a lot more ,much more grip and she would leap from 15-30 knots much faster.

when i bought them i was understood to believe that a SS prop increases the revs by upto 200rpm as the prop is more effecient in the wtaer and also has more mass to spin so will spin faster

My current boat is under pitched slightly as it was set up for carrying load so i could go to 23" and maybe just nudge 50 knots but i run the prop that came with it 21.5 and hit 47 on my own but can still do 45 with 6 people in
good luck
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Old 15 September 2008, 03:53   #15
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Quote:
Originally Posted by behavin View Post
when i bought them i was understood to believe that a SS prop increases the revs by upto 200rpm as the prop is more effecient in the wtaer and also has more mass to spin so will spin faster
More mass takes more energy to spin, so will spin slower for a given power input.

jky
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