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Today was the last straw for my Berkley B cut aluminum impeller. I started the boat up at the river and got out to the channel and started to get on it....but soon after the boat started vibrating as if there were a rock or something lodged in the pump. To make along story short. I'm pushing 650hp and I knew that the Aluminum impeller wasn't going to make it much longer. After taking it apart I found many stress cracks and it's basically junk. My question is what cut of stainless should I replace it with. I have only been able to take the boat to the top end a few times and I hit 81mph but I forgot to check the RPM. I'm thinking of going to an A but if I'm spending that much cash I want it to be the right one. Any suggestions on how to choose? Also what's the difference between the A, A2, A3, and A4?
One more thing I am now concerned about the shaft itself. I have no idea if it is a hardened steel shaft but I don't want that to be next. A friend of mine had one twist on him with 700hp. Are there any markings on them that indicate if they are hardened or not?
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If you were happy with the performance ... stay with what you have (although if you go from a Berk impeller to an aggressor you need to drop a size. Aggressor runs the blades all the way to the front edge which makes it a cut size larger in water flow. (An Aggressor B matches behavior of a Berk A) If you want lower RPM (by something like 500) and a better holeshot then size up a cut, or a half-cut (A-B) to drop 200 to 250 or so.
According to Jet Boat Perf Calculator, 650 HP spins a Berk B at 6223 RPM.
I'd go to an A personally, Drops top RPM to 5900 Will drop your speed likely tho.
You can save 300 bucks by going Mag-Bronze if you want. I am considering it.
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Do you have any idea where that 650 hp is rpm-wise. That's what you need to consider when selecting an impeller cut. Rpm you could turn before would also help in making a decision. Each size should drop you around 200 rpms until you hit your hp peak.
Where's that impeller chart at?
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The impeller that I had in it was an agressor B. So are you recommending a Berkley A? It pisses me off but every time I had a chance to top the boat out (which was very seldom) I was looking at the MPH instead of the RPM. Now it's too late because I have no impeller to check it with. I know I hit 81 MPH and it wasn't pulling anymore. I'm wondering if I step up to an A if that will get me a little more? I just don't want to go spending that much money and get poor performance out of it.
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If all you have is a speed, you don't have enough info to make a decision. Better just stay where you're at. Maybe next time.
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I hear what you are saying. It's just that I'd like to get the best fit......hard to do if I don't know the other part of the equation. Any answers for me on the race shaft? Is there a way to tell if it's a hardened shaft or not just by looking at it, markings etc., or do you have to have it hardened tested?
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get an A, if its too big cut it.
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Which brand? :D
The shaft is stainless right?
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So you are saying a berkley A? It is stainless yes but I don't know if it's hardened. I buddy twisted his but he caught it in time and didn't break it but the splines are definitley twisted. I would think they would put a stamp on them showing if they are or aren't.
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