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what impeler did the stock Berkeley 12-JC come with, and what is the diference between all these differendt impelers, from my understanding it is like gears on a car, the higher numericaly, better holeshot, higher rpm's at higher speeds, lower number gear, higher speeds at loewer engine rpm's. So basicaly what my question is is what impeler gets you what ??
On the top of the suction housing right over the bearing, there should be a plate that tells you the model of your pump then the impeller cut. Most say JC-A Meaning its a JC pump with an A-cut impeller.
You mentioned cars. do you understand Torque Converters in Automatics?
Similar hydraulic principles apply here.
Unlike props, impellers all have the same 'pitch'. they do however have different lengths. Impellers are named A, b, C etc depending on how much is cut off of the backside of them, closest to the vanes in the bowl.
You should choose an impeller cut that allows your engine to operate in its peak TORQUE range.
Generally each cut of the impeller results in a 500rpm increase in engine speed.
so different props dont necessarily get you "holeshot" or "topend" they just let your motor operate in different rpm's, right ?
Getting your engine to operate in its proper range should result in better hole shots AND better top end.
Think about it...You hit the gas in a Jet and it revs as high as its torque will let it...Instantly. wheather from a dead stop or from cruise. It will hit the same RPM and not climb.
So.
If you put a Double A impeller (AA) on a stock engine, it will likely only rev to say 4000 rpm. Put an 'A' in it... see approx 4500. choose a 'B' and hit nearly 5000
What RPM that you NEED to be at is dependant upon your engine specs.
Impeller selection lets you tune the pump to the engine.
those little shits are expensive too ha ?
They're only real expensive if you want to go "up" in impeller length. You can have your imeller cut to a smaller size like an A to a B for example.