hey guys gotta newbie question here I've had my boat for couple years now finally blew up so what started out as just rebuild turned into stroker, heads, etc and just having engine built so now I have my first legit non junk yard build engine I wanna freshin the pump i have a 12JG with supposed to be an A I haven't got a good explanation on how to calculate impeller I kno JBP has the calculator but what do I need to kno exactly it's a lake cruz/ local race night boat engine goin to dyno in week or so I kno I need dyno info also I seen a chart does this mean anything to someone that knows what there lookin at? Long post sry guys

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When you dyno the motor you will know what RPM peak HP is . If you have an A cut already run it at see where it wants to rum rpm wise . If the a. It is not letting it run enough rpm go with a smaller cut impeller if it runs to high of a rpm go with a bigger impeller. You want it to run wide open at peak Hp Rpm.


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Make sure you get uncorrected HP numbers.

Also, a bigger/heavier boat will need a larger cut impeller.

Cheers,

Joe

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What's the difference between corrected and uncorrected HP?  And why would he want that instead of the other?


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As always, thanks for the info Glenn...  Also, thanks for the info on the races this weekend, hope to see you out there on Sat


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River rat when u say smaller cut is that a B bein smaller than A? I'm gonna see how it acts with what it has now but want the whole combination to wrk so I'm just preparing myself yo buy impeller cause everyone knows how it goes building these things

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AA is larger then an A cut . B is smaller then an A and so on ...


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