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Old 06 May 2022, 16:56   #1
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4 blade prop vs 3 blade

Hello
Any propeller gurus in here?
I have a Revenger 27 with a Suzuki 300, previously had a 24p 4 blade prop and was hitting 48 knots at 6300rpm.
I’ve just fitted a 26p scorpion 3 blade prop and hitting 48 knots at 6050rpm but the boat is feeling unstable at wot.
My guess is this new prop is giving too much stern lift causing a bit of chimewalking?
I went for the 3 blade prop to get a bit more top end speed and hopefully improve fuel economy but now thinking of going back to the 4 blader
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Old 06 May 2022, 18:08   #2
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Originally Posted by Alexwalms View Post
Hello
Any propeller gurus in here?
I have a Revenger 27 with a Suzuki 300, previously had a 24p 4 blade prop and was hitting 48 knots at 6300rpm.
I’ve just fitted a 26p scorpion 3 blade prop and hitting 48 knots at 6050rpm but the boat is feeling unstable at wot.
My guess is this new prop is giving too much stern lift causing a bit of chimewalking?
I went for the 3 blade prop to get a bit more top end speed and hopefully improve fuel economy but now thinking of going back to the 4 blader


I’m a big fan of 4 blade props, every RIB I’ve owned always felt more “planted” with a 4 blader. Dunno if that’s my imagination or reality. That said, 4 bladers generally give more stern lift, which puts more of the keel in the water & (imho) adds to the grip, whilst taking a bit off the top end. Which is what you’ve discovered. I’ve tried a few 4 blade props over the years & the “best” I’ve found is the Mercury REV4 which was recommended to me by the legendary Mike Vincent of South Coast Marine.
All my opinion naturally.
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Old 06 May 2022, 18:48   #3
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Yea the 4 blade seemed a lot more stable…. I could bang it up to wot and it was very planted….. I’m thinking about sending it to steel developments to have it put up 1 pitch to drop the revs a bit and put it back on.
I’ll do some more testing first with this 3 blade to see if I can make it more stable with the trim tabs/ less trim first.
The boat also seems to lean to port more under acceleration than the 4 blade did too… guessing a bit of prop torque causing this
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Old 06 May 2022, 19:40   #4
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Yea the 4 blade seemed a lot more stable…. I could bang it up to wot and it was very planted….. I’m thinking about sending it to steel developments to have it put up 1 pitch to drop the revs a bit and put it back on.

I’ll do some more testing first with this 3 blade to see if I can make it more stable with the trim tabs/ less trim first.

The boat also seems to lean to port more under acceleration than the 4 blade did too… guessing a bit of prop torque causing this


4 bladers can run higher than 3 bladers. This can mitigate the lean to port. The lower the engine the more pronounced the lean to port…generally.
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Old 14 May 2022, 06:27   #5
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Originally Posted by Pikey Dave View Post
4 bladers can run higher than 3 bladers. This can mitigate the lean to port. The lower the engine the more pronounced the lean to port…generally.
Sound advice.
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Old Yesterday, 16:50   #6
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Hole shot vs top end speed. Also all about the pitch, which ca determine hole shot vs top end.
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