Cavatation??
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Cavatation??

  1. #1
    Living in a cage of fear thatguy's Avatar
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    Default Cavatation??

    So... took the Miller out Sunday. Engine runs GREAT!!

    Last year, the boat pulled hard, topped at 70MPH at 5200 RPM.

    Now, at around 60 MPH , it starts to "rattle" and vibrate, and the engine "revs". I am certain that it is cavitation.
    As soon as you let off, it stops and will cruise like a swiss watch right up to 60 or so. There is PLENTY of motor left, just wants to suck air.

    When I had the intake reset this winter, I did notice that the "spoon" or lump before the grate on the bottom had been removed.
    Is this generally enough to cause cavitation at speed?
    The pump mods were a droop and Hyd. place, new detailed A/B. No shoe or plate.

    It doesn't matter where I trim it, at 60 MPH it breaks loose.

    The boat wants to go, and I am certain it will pull hard far past 70 MPH comparing it to how it ran last year.

    So.. Is the removal of the "lump" on the bottom capable of causing this? If so, how should I build it back?

    I have had this boat for 3 years, 3 different engines and have NEVER had it cavitate before now.
    Last edited by thatguy; 05-19-2009 at 08:54 PM.
    Tommy
    Quote Originally Posted by Rexone View Post
    Tommy please remove all Jimsplace quotes from your sig and don't put more back. He doesn't like it and it is against the rules. Thank you.
    "So as through a glass, and darkly
    The age long strife I see
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    Many names, but always me."

    Gen. George S Patton

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  3. #2
    Senior Member H20MOFO's Avatar
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    I could be way off here...but I'd guess your new intake is set at the wrong angle, or you're sucking air through the sides of it. Why else would it have worked o.k before the new intake(reset)????
    Another Hot Boat refugee

  4. #3
    Living in a cage of fear thatguy's Avatar
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    Quote Originally Posted by H20MOFO View Post
    I could be way off here...but I'd guess your new intake is set at the wrong angle, or you're sucking air through the sides of it. Why else would it have worked o.k before the new intake(reset)????

    Thats why I was wondering if the removal of the "lump" during the reset would make a difference?

    The intake was not relocated, just pulled and resealed, to my knowledge.

    Something ain't right.
    Tommy
    Quote Originally Posted by Rexone View Post
    Tommy please remove all Jimsplace quotes from your sig and don't put more back. He doesn't like it and it is against the rules. Thank you.
    "So as through a glass, and darkly
    The age long strife I see
    Where I fought in many guises,
    Many names, but always me."

    Gen. George S Patton

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  6. #4
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    Default ?

    Why was the lump removed??

  7. #5
    21 Daytona Outlaw's Avatar
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    Default

    and who did the reset?
    #55

  8. #6
    Living in a cage of fear thatguy's Avatar
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    Quote Originally Posted by 1hotboat View Post
    Why was the lump removed??
    That is a very good question. I did not want it removed. I understand its purpose, and was concerned from the moment I saw it was gone. that could be why i am sort of focusing on that.
    Tommy
    Quote Originally Posted by Rexone View Post
    Tommy please remove all Jimsplace quotes from your sig and don't put more back. He doesn't like it and it is against the rules. Thank you.
    "So as through a glass, and darkly
    The age long strife I see
    Where I fought in many guises,
    Many names, but always me."

    Gen. George S Patton

  9. #7
    Senior Member DuaneHTP's Avatar
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    Bump removal could easily be your problem.

  10. #8
    Living in a cage of fear thatguy's Avatar
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    Quote Originally Posted by DuaneHTP View Post
    Bump removal could easily be your problem.

    Any tips on rebuilding it? 79' Miller Jet.
    Tommy
    Quote Originally Posted by Rexone View Post
    Tommy please remove all Jimsplace quotes from your sig and don't put more back. He doesn't like it and it is against the rules. Thank you.
    "So as through a glass, and darkly
    The age long strife I see
    Where I fought in many guises,
    Many names, but always me."

    Gen. George S Patton

  11. #9
    Resident Ford Nut Sleeper CP's Avatar
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    Wow Tommy,

    That sucks, so who removed the spoon ?

    S CP

    "Dark Sarcasm"
    Going fast is only half the fun ... what you make go
    fast is the other half.
    " A Government big enough to give you everything you want is big enough to take away everything you have"

  12. #10
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    Default Intake

    I would be pissed I would go back to the guy and see WTF was up with the removing the spoon.... and If he has a clue to what he doing, make he redo the bottom or pay to have it redone. You know why it was there "to improve the loading of the pump" If I understand it right.IMO it if the pump could suck air from intake to suction housing it would leak water?

  13. #11
    Living in a cage of fear thatguy's Avatar
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    Quote Originally Posted by Sleeper CP View Post
    Wow Tommy,

    That sucks, so who removed the spoon ?

    S CP
    Yeah, it sucks big time.

    I busted my ass every day (9 days, 12 hours a day) on my days off to finish the entire boat. re-carpeted, entire replumbing the water system, built all new braided lines, finished the engine and installed it with the new headers, installed the Jet, new place, all controls new, finished up at noon on Sunday and was on the lake at 2:00.
    Left for work Monday morning.

    Rather not say who did the intake, but wish I had done it myself, or just left it alone.

    but what I really need to know is how to go about rebuilding that bump. I will start with that, and am sure it has to be a factor.
    Even if you just creep up on the GPS, at 60 it spins its wheels.

    I'll get it back, just a little disappointing after all that work and $.
    Tommy
    Quote Originally Posted by Rexone View Post
    Tommy please remove all Jimsplace quotes from your sig and don't put more back. He doesn't like it and it is against the rules. Thank you.
    "So as through a glass, and darkly
    The age long strife I see
    Where I fought in many guises,
    Many names, but always me."

    Gen. George S Patton

  14. #12
    Senior Member Brendellajet's Avatar
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    Is this a miller V bottom? Plenty of them around here...dont think any have spoons though...
    "He is a lover, not a fighter. But he's also a fighter, so dont get any ideas."

  15. #13
    Impeachment! 75 TX's Avatar
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    Quote Originally Posted by Brendellajet View Post
    Is this a miller V bottom? Plenty of them around here...dont think any have spoons though...
    My '75 didn't

  16. #14
    Senior Member jetboatperformance's Avatar
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    Mine runs Hard (80) with a jacuzzi WJ , no spoon no Bump,same bottom as yours , curious to see some pics Tommy ! Tom

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