Finally Blew It and Need Help!!

[Lawler]

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?

[SmokinLowriderSS]

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.

[malcolm]

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?

[Lawler]

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.

[malcolm]

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.

[Lawler]

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?

[BrendellaJet]

get an A, if its too big cut it.

[malcolm]

Which brand? :D
The shaft is stainless right?

[Lawler]

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.

[Blown Spectra]

check your PM's
eric

[Lawler]

My PM's?

[MikeF]

Today was the last straw for my Berkley B cut aluminum impeller.
The impeller that I had in it was an agressor B.
Soooooooo.......Which kind was it? :hammer2:

[Lawler]

I'm sorry....it's an agressor B not a Berkley B. Any suggestions?

[MikeF]

What engine and how much cam?

[bp]

check the shaft with a magnet. if it's ss, no sticky. if it's ss/alloy (hard), the magnet will stick.

[Lawler]

Com P Cams Mechanical Roller (292/298 advertised duration, 254/260 duration @ .050”, .660”/.666” lift, 110 lobe separation)
496 BB Chevy, Mighty Demon Carbs: (Dual 650 CFM Vacum Secondary 4 Barrels)
Dart Pro 1 Aluminum (310 CC Intake Chamber, 2.250” competition stainless intake valves, 1.880” inconel exhaust valves, comp cams double valve springs, 10 degree locks and retainers, ARP Rocker Studs, Comp Cams guide plates)

[MikeF]

If it is not a race boat, I'd start w/an AA. You'll have good perfomance and be a little more economical too by not turning a higher rpm.
If you find you want more rpm you can cut it to an A, but you might find that you don't gain any speed...only rpm (not always the case).
You have enough power to turn those impellers pretty good.
I'd stick with a Legend impeller. The quality is there to begin with.
If you find a used Berk SS impeller in good shape, that would be a good choice too.