What's the rpm at WOT and about how much horsepower do you have? If you know that, then we can predict what impeller you have based on a chart. The chart is really used for estimating horsepower when you know the impeller cut and rpm. But it can also be used to predict an unknown impeller cut, as long as you know the other two variables.
But the only true way to know the impeller cut is to take the bowl off and look at the back of the impeller (it should be marked). And the best way is to measure the diameter of the vanes because it may have been cut and not remarked.
Great pump, used in many race boats. With the right internals, they can take as much horsepower as you can throw at them. But even with stock internals, they can take a pretty good amount of power.
