Generally, cast aluminum impellers are able to withstand up to 500HP and 5500 rpm as long as the jet boater keeps the jet drive loaded properly and does not over rev the drive.  Unlike the cast aluminum, Mag/bronze and stainless steel impellers are able to handle greater horse power loads and high speed unloading conditions.  But, just a word to the wise, loading, unloading and then reloading your Jet Drive on a high horse power blast run will create tremendous pressures inside your drive unit.  You will eventually experience catastrophic jet drive failure if you don't correct the problem.  No matter how good the parts are in your Jet drive, you will tear them up.

Now, I know that a bunch of jet boaters out there run cast aluminum impellers at much higher HP loads and get away without troubles.  If you want to stretch the limits of cast impellers, that is up to you.  It depends a lot on what kind of a jet boater you are, as to how much you can over power cast aluminum impellers and get away with it.  As a builder, I have to be conservative and put my emphasis on durability.  I use 500 HP and 5500 RPM as my cut off point.  

For you folks running with a lot of horse power, the proper impeller cut and proper intake hardware for your application is a must.  Keeping an eye on your suction housing pressure is not a bad idea either.  If you are racing in a shallow, rocky environment and gulping a lot of air, the stainless steel or 1018 billet steel impeller will take the biggest beating.

These impellers are nicely cast at A/T's own foundry.  They are nicely finished and heat treated.  I am comfortable using the cast aluminum impellers up to 500HP.  A/T impellers for the A/T jet have a wear ring skirt on the back side of the impeller that fits into a machined surface in their bowl.  I call this a stuffer skirt.  This is a nice design and for this reason I recommend using only A/T impellers in A/T jets.  I have seen builders use other impellers on A/T jets but to me, this makes no sense, as you give up the anti turbulence design of the stuffer.  A/T impellers run a real good profile anyway, so why not use them in your A/T jet.  If you have a preference for an impeller by another manufacturer, they will fit the A/T but you will give up the stuffer skirt design.  If you do use another manufacturers impeller and wish to have a stuffer, you will have to fit a stuffer plate into the A/T bowl.  The newer Dominator uses the A/T impeller also.  Ron Gordon owned Dominator before he designed the A/T jet drive.  A/T jet drives have reached speeds of 163 MPH and have run 126MPH on the white water racing circuits.  A/T also makes impellers for Berkeley, Aggressor and Legend style jets.  It is the same A/T was the first company to offer the 9.250 and 9.500 impellers.

These impellers are cast at Aggressors foundry.  These impellers incorporate a greater front side vane angle than other impellers.  They also have a slightly wider mouth opening, by a .060", (approx.) over other impellers. They also have a longer, flatter release angle on the back side of the impeller. They will load your motor approx. 200-400RPM harder than the Berkeley impeller power curve chart for any particular cut.  These impellers are nicely cast and they are heat treated and balanced.  I prefer to hand detail the aluminum impellers when I use them on my blue printed jet rebuilds.  I am comfortable using these aluminum impellers up to 450 HP.  Any thing over 450HP I prefer to use Aggressors Mag/Bronze impeller which can handle very high horse power loads.

Aggressor has had tremendous success with their Bronze impellers, especially their B cut profile.  This impeller works great on high HP, naturally aspirated, lake boats.  I have used the bronze with great success myself.  The Aggressor bronze has reached speeds of 145 MPH.  

At Aggressor, Dave is always working to improve his product line.  The latest batch of Mag/Bronze impellers are the best yet. Note* If you plan to use a shouldered wear ring you must use the Aggressor shouldered ring to avoid axial interference with the impeller.   The Aggressor Impeller wear ring skirt is approx.  .055" narrower than that of other impellers.  Therefore, the Aggressor shouldered wear ring is designed to fit the narrower impeller skirt.  You can use the Aggressor shouldered ring on the other manufacturers' impellers without a problem.

These impellers are cast at Berkeley's foundry connection.  These impellers are nicely cast, CNC machined and hardened.  The finish is good and I am comfortable with the aluminum casting to 500HP.  Any more HP and I would suggest a stronger impeller.  Berkeley has their own stainless impeller profile.  Impellers from other manufacturers will fit as well.

Jacuzzi Marine Jet made two jet drives for the recreational boater, the WJ and the YJ.  The WJ is a dual flow jet incorporating a five vane cast aluminum impeller.  The YJ is an axial flow jet with a large stainless impeller that produces a lot of mass flow and was designed for heavy boats utilizing up to 300HP.  Both of these jets can be upgraded with the energizer kit prices on my Jacuzzi page.  Jacuzzi is now owned by North American Marine Jet, Inc. in Benton, Arkansas.  The impeller for the WJ is a good casting that works fine out of the box and is cast at NAMJ's own foundry.  These impellers are more expensive than other aluminum impellers and are sometimes hard to get on a short notice.  At this time I don't believe that Jacuzzi is producing the WJ and hasn't for some time.  For this reason some parts are getting hard to come by.  Nevertheless, in its day, there were a lot of racers that could tweak 100MPH out of the WJ pump.  

These impellers are cast at Legends own factory connection in Richmond, California.  These impellers are nicely cast with a nice finish.  Legend calls their cast aluminum impeller its "factory blue print."  Dave, at Legend, has told me that he uses cast iron molds for his impellers instead of sand castings.  These molds make for a more consistent casting as a result.  These impellers are heat treated 356-T6 Aluminum and are sharpened, balanced and usually ready to go right out of the box.  These impellers also have a coarser front side vane angle and will load 100-200 RPM harder than the Berkeley.  I am comfortable using this impeller up to 500HP.  I have used this impeller with great success.

NOTICE TO ALL JET BOATERS:  As of March 2007, Legend Jet Drive is no longer in business.  Legend Jet Drive has been bought by American Turbine.  I talked to Ron at A/T and asked if he was going to keep the Legend impeller profile and he informed me that he was going to run some tests before he makes his decision.  In the mean time, these impellers will be available until the stock runs out.

Precision Jet Drive aluminum impellers are the only impellers on the market that are CNC machined from a solid bar of forged aircraft quality aluminum.  These impellers are heat treat hardened and balanced.  They come perfectly smooth and finished right out of the box.  These impellers are CNC machined in two pieces, the hub and the shroud.  These two pieces are then furnace welded together and then tig welded.  The vanes are set up on a more aggressive pitch angle and will load your pump harder.  The power curve is similar to the Legend curve.

Don't let the weld lines fool you, this impeller works just fine. I am comfortable using this impeller to 650 HP and have done so very successfully with no problems so far.  PJD also offers a CNC machined axial flow inducer impeller. I use this inducer exclusively.

I sell impellers for Panther Jet and Kodiak Jet.  On the multi stage jets, like the Kodiak Jet, there are a number of impeller combinations that can be used.  These combinations are based on your personal application requirements.  Call for application and pricing.