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Old 05 September 2010, 03:31   #1
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prop

Hi, guys anyone know the calc to obtain correct prop, going from a 3 blade to a 4 blade. as have a 5.6 boat with a 115 4 stroke max 6000 revs, at the moment i have a 14x21 3 blade. and i want to get the revs down as i can rev over max with this prop cheers guys...
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Old 05 September 2010, 04:33   #2
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Originally Posted by searover View Post
Hi, guys anyone know the calc to obtain correct prop, going from a 3 blade to a 4 blade. as have a 5.6 boat with a 115 4 stroke max 6000 revs, at the moment i have a 14x21 3 blade. and i want to get the revs down as i can rev over max with this prop cheers guys...

Poss not the answer you are looking for, but on recommendation from here i spoke to the very helpful lady at 'Steel Developments' for advice (do a search on here)....who came up trumps!

Dan
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Old 05 September 2010, 04:52   #3
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It's all guesswork really but if you're going from a 3 to a 4 blade then sticking with 21" should bring your revs down by 200-300. The increase in surface area usually has a similar effect to increasing the pitch by 2".
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