impeller cut question
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impeller cut question

  1. #1
    Senior Member sandeggo's Avatar
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    Default impeller cut question

    boat specs.
    16'
    350 (.30) over
    mild rv cam
    big valves (2.02)
    650 holley
    hei
    spun a old wore out pump with an "A'' impeller to 4400 rpm.
    havent had the motor on a dyno, but i am rebuilding the pump right now. would it be safe to say that starting with a "b" cut would be a pretty good choice to pick up a little more rpms?

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    Senior Member DuaneHTP's Avatar
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    Just really depends upon how bad your old pump was. But, yes, it should be a good place to start.

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    Senior Member GAWnCA's Avatar
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    Are there any visuals as ro what the differnt cut impellers look like? I've often wondered, what is cut to make the difference.
    Wags

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    Senior Member GT Jets's Avatar
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    Quote Originally Posted by GAWnCA View Post
    Are there any visuals as ro what the differnt cut impellers look like? I've often wondered, what is cut to make the difference.
    I actually have an impeller cut chart, I will try to scan it when I get to use my computer

    They cut the trailing egde, making the vanes (aka blades) shorter.....

    I am sure someone will beat me like I owe them money on the scan thing..But I will try to beat them to the punch...

    GT
    GT


    Quote Originally Posted by Quickjet View Post
    Put a 300 on the back of it, Flywheel it and a nosecone. $15,000 later you'll have a 65 mph pile of shit......

  7. #5
    Senior Member sandeggo's Avatar
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    Quote Originally Posted by DuaneHTP View Post
    Just really depends upon how bad your old pump was. But, yes, it should be a good place to start.
    the old pump and impeller were pretty dang bad. there was alot of cavitation marks in the impeller.

  8. #6
    Senior Member sandeggo's Avatar
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    Quote Originally Posted by GT Jets View Post
    I actually have an impeller cut chart, I will try to scan it when I get to use my computer

    They cut the trailing egde, making the vanes (aka blades) shorter.....

    I am sure someone will beat me like I owe them money on the scan thing..But I will try to beat them to the punch...

    GT
    glen i have seen alot of impeller charts, but since i dont know my actual horsepower, i didnt really pay to much attention, i wanted the "pros" opinion

  9. #7
    Seriously off center slowride's Avatar
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    My concern is that you have a RV cam (torque not RPM), and big valve heads but you want to spin more rpm. If you want more rpm and take advantage of the heads, consider more lift in the cam.
    My .02

  10. #8
    Senior Member jetboatperformance's Avatar
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    Quote Originally Posted by slowride View Post
    My concern is that you have a RV cam (torque not RPM), and big valve heads but you want to spin more rpm. If you want more rpm and take advantage of the heads, consider more lift in the cam.
    My .02
    Times 2 also what pistons/compression ratio ?

    ps heres some info for ya courtesy of AT


    H.P. 9.5 9.25 AA A B C
    150 2900 3050 3200 3600 3800 4050
    200 3200 3350 3500 4000 4200 4450
    250 3450 3600 3700 4300 4500 4800
    300 3800 3950 4050 4550 4800 5100
    350 4050 4200 4300 4750 5100 5350
    400 4250 4400 4500 5050 5300 5600
    450 4450 4600 4700 5250 5500 5850
    500 4650 4800 4950 5400 5700 6050
    550 4800 4950 5100 5550 5850 N/A
    *THESE RPM VALUES MAY VARY ACCORDING TO HOW YOUR BOAT ALLOWS THE PUMP TO LOAD
    HORSE POWER REQUIREMENTS ARE AT THE PUMP SHAFT

    AMERICAN TURBINE JET DRIVE IMPELLER SPECIFICATIONS
    IMPELLER SIZE LARGE DIAMETER SMALL DIAMETER MACHINED ANGLE
    9 1/2" 9-1/2" 8-1/4" 25 DEGREES
    9 1/4" 9-1/4" 8-1/4" 20 DEGREES
    AA 9-3/32" 7-13/16" 25 DEGREES
    A 9" 7-1/4" 30 DEGREES
    B 8-3/4" 6-3/4" 33-1/2 DEGREES
    C 8-1/2" 6-1/2" 33-1/2 DEGREES

  11. #9
    Senior Member GT Jets's Avatar
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    Quote Originally Posted by sandeggo View Post
    glen i have seen alot of impeller charts, but since i dont know my actual horsepower, i didnt really pay to much attention, i wanted the "pros" opinion

    Yeah I figured you have. I was trying to answer Gregs "cutting the impy" question...It was a shameless thread jack.

    More RPM BTW does not necissarily mean more HP like Tom and slowride state, you will find that the performance of the pump is generally centered around the 5000 RPM mark, they will work at higher and lower RPM, but the curve really drops off, I like to stay near 5K for a BBC and 5.5K for a SBC as a general rule for "family boat" type apps...Just my preference from what I have learned by making assumtions and mistakes...

    GT
    GT


    Quote Originally Posted by Quickjet View Post
    Put a 300 on the back of it, Flywheel it and a nosecone. $15,000 later you'll have a 65 mph pile of shit......

  12. #10
    Member MRUSER's Avatar
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    Ok so if you want to play around with the impellers is it as simple as pulling one out and putting another in Or do you have to change wear rings to mach each impeller?

  13. #11
    Seriously off center slowride's Avatar
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    Quote Originally Posted by GT Jets View Post
    Yeah I figured you have. I was trying to answer Gregs "cutting the impy" question...It was a shameless thread jack.

    More RPM BTW does not necissarily mean more HP like Tom and slowride state, you will find that the performance of the pump is generally centered around the 5000 RPM mark, they will work at higher and lower RPM, but the curve really drops off, I like to stay near 5K for a BBC and 5.5K for a SBC as a general rule for "family boat" type apps...Just my preference from what I have learned by making assumtions and mistakes...

    GT
    I hope Sandeggo doesn't miss the point as you did. It's not about "horsepower" (let's not get into a hp/torque thread again), it's about the cam not providing enough lift for a fully loaded engine at a higher rpm. That's why I didn't mention duration or lobe center (though they are also a consideration)..... my concern is that it'll wheeze without enough lift.

  14. #12
    Senior Member sandeggo's Avatar
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    10:1 is the compression ratio and the only thing i know about the pistons is that it is bored .30 over making it a 355. this is all going off of the previous owner, and the seat of the pants. dont know if it helps or not, but the boat gps'ed at 58.7 before the gps shut off

  15. #13
    Senior Member jetboatperformance's Avatar
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    Quote Originally Posted by sandeggo View Post
    10:1 is the compression ratio and the only thing i know about the pistons is that it is bored .30 over making it a 355. this is all going off of the previous owner, and the seat of the pants. dont know if it helps or not, but the boat gps'ed at 58.7 before the gps shut off
    Do you know if this is a "flat top piston deal" and are they Old camel hump heads ? Tom

  16. #14
    Senior Member sandeggo's Avatar
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    Quote Originally Posted by jetboatperformance View Post
    Do you know if this is a "flat top piston deal" and are they Old camel hump heads ? Tom
    Tom they are the humps, I don't know if they are flat

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