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  1. #1
    Junior Member tunnelmann's Avatar
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    Default Need Help

    I picked this little jet boat up for the wife It has a Nissan 4 cyl in it
    Had a cracked head so I replaced it First time out & it won't get up on plane motors taching 6 grand I pulled the back half of pump off & the impellar is perfect not a nick in it Anyone have any ideas what could be wrong with it????

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  3. #2
    Hondo Jet blown540's Avatar
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    Wow, that's a head scratcher. It's either cavitating due to a restricted intake or there is somthin funky going on with the powertrain. Is there a key in the impeller? I don't know what's in between the motor and the impeller but I would be finding out. Good luck

  4. #3
    Senior Member Need4Speed77's Avatar
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    Quote Originally Posted by tunnelmann View Post
    I picked this little jet boat up for the wife It has a Nissan 4 cyl in it
    Had a cracked head so I replaced it First time out & it won't get up on plane motors taching 6 grand I pulled the back half of pump off & the impellar is perfect not a nick in it Anyone have any ideas what could be wrong with it????
    Check the packing in the pump, if you are sucking air then you won't go anywhere, lube it up and tighten the packings a turn or so and that might help.

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  6. #4
    Sit N' Spin Jetaholic's Avatar
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    Or you might have something stuck in the pump. Also the pump could just be in need of a rebuild as well.



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  7. #5
    Junior Member tunnelmann's Avatar
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    Quote Originally Posted by Need4Speed77 View Post
    Check the packing in the pump, if you are sucking air then you won't go anywhere, lube it up and tighten the packings a turn or so and that might help.
    Where is the packlng? I don't know sh!t about jet pumps but it felt to me like it was cavitating/sucking air

  8. #6
    Senior Member Brendellajet's Avatar
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    does the boat move at all?

  9. #7
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    Get under the back of the boat and look up into the intake of the pump is there anything stuck up in there?

  10. #8
    Junior Member tunnelmann's Avatar
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    Quote Originally Posted by Oldelmn8tr View Post
    Get under the back of the boat and look up into the intake of the pump is there anything stuck up in there?
    I said I don't know sh!t about jet pumps But I'm not frikin stupid
    & yes it moves just won't get on plane

  11. #9
    TRG
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    any pics of the rear or anything other than the front in the driveway?...looks like it would be fun to goof around with!
    P.S. dont take any sort of offence to that!

  12. #10
    Junior Member tunnelmann's Avatar
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    Quote Originally Posted by toddnjuzz View Post
    any pics of the rear or anything other than the front in the driveway?...looks like it would be fun to goof around with!
    P.S. dont take any sort of offence to that!



  13. #11
    TRG
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    Quote Originally Posted by tunnelmann View Post


    I would be waaay interested in seeing the inside of that Doen pump, does the thrust line seem a bit high to anyone else??

  14. #12
    Owner/Crew Chief 1/4 Miler's Avatar
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    Just a guess, but, looks like too much weight too far back combined with too little thrust being generated by that small DOEN Pump ... a much longer, lighter weight ride plate might help some, but, don't expect too much due to the weights & balances with that small pump (lack of thrust proportional to the CG). You may never be able to 'get it up on plane' due to what it is and may have to settle with just a 'putt around' ..... which isn't a bad thing and has its use.

    Something you might want to try to increase the thrust 'a bit' is to put a restriction in the nozzle to decrease its size a little ... going to be difficult requiring 'one off' piece(s) as those old DOEN Pumps are not set up for nozzle inserts.
    Last edited by 1/4 Miler; 08-25-2008 at 01:50 PM.

  15. #13
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    The boat appears to be a production piece and not a one off piece, so I would believe that it should at least get up on plane in new condition.

    We have eliminated the simple stuff, blocked intake etc.

    Next need to ensure that the driveline is in proper working order - no slipping coupler, all drive keys in place. What sort of coupler does this pump use? If a u-joint driveline like Berkeley, nothing to slip, if a rubber coupler like an I/O then that could be a problem.

    From what little I could find on the internet, the Doen pump is an axial flow pump (like Jacuzzi YJ). I would be looking to verify the clearance between the impellor and housing is withing spec. What is spec? I would guess around .015", but don't really know.

    Doug

  16. #14
    I never hit bottom. 79Challenger's Avatar
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    I don't have any input on your problem but I just wanted to say, "Cool boat!"

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