550sx Coupling Damper Install Direction
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  1. #1
    PWCToday Newbie
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    550sx Coupling Damper Install Direction

    - 1990 550sx
    - Solas 14/19 impeller
    - New pump bearings and seals


    Does anyone know why the coupling damper between the engine and driveshaft couplers needs to be installed with the cavity side forward? I have been having issues with the jet pump shaft threads stripping, causing the impeller to float around inside the pump case. I noticed the coupling damper was installed backwards during the most recent teardown. Before installing a replacement jet pump shaft, I'd like to understand why the threads are getting stripped. Everything else seems to be installed properly.
    2020-09-12 13.51.51.jpg

    Thanks!
    Last edited by mvr1212; 09-12-2020 at 05:29 PM.

  2. #2
    PWCToday.com Is My Home Away From Home Bionic racing's Avatar
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    Re: 550sx Coupling Damper Install Direction

    On full circle 400/440s they had a bolt to hold the taper iron coupler on crank, so that cove was to make room for the bolt at the end of crank , never changed desighn

  3. #3
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    Re: 550sx Coupling Damper Install Direction

    Ok, thanks. I can probably rule out that being the cause to my thread stripping issue.

  4. #4
    PWCToday.com Is My Home Away From Home Bionic racing's Avatar
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    Re: 550sx Coupling Damper Install Direction

    10/4 ,is your mid shaft housing centered good , square with motor ? New impellor or used one ? Is that an aftermarket shaft ?
    Last edited by Bionic racing; 09-12-2020 at 10:15 PM.

  5. #5
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    Re: 550sx Coupling Damper Install Direction

    I am going to reassemble everything and take a different approach than before. The impeller was new. Slightly chewed up leading edges now because of the thread issue.

    Although everything measures fine (straight edge across couplers and feeler gauge in coupler gap), I did not loosly tighten the shaft housing and align everything BEFORE torquing it down. I'll plan to get it all aligned, then torque when reinstalling. All clearances, measurements, and rotation seemed to be fine during the last installation, so I went ahead with it.

    Another interesting thing that may indicate a mis-alignment is that the section of the drive shaft inside the hull gets really hot when running it on a garden hose. The section outside the hull does not. I'm guessing it's mis-aligned in the shaft housing and rubbing causing it to get so hot.

    I came across a post somewhere at one point related to this topic, but can't seem to find it again.

  6. #6
    PWCToday.com Is My Home Away From Home Myself's Avatar
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    Re: 550sx Coupling Damper Install Direction

    It does sound like you may have something in a bind.
    http://www.facebook.com/twinlakesjetskirepair

    '89 Kawi 650SX 42.4 GPS
    +3" stock pipe, ported ex. manifold, drilled waterbox, blueprinted pump, Ocean Pro ride plate

    '99 Yama GP1200 65U 61.8 GPS
    ported cylinders, matched cases, milled head, blueprinted pump, long ride plate

    '96 Seadoo HX 717 53.13 GPS
    light porting, massaged cases, lightened flywheel, port matched manifolds, Rossier pipe, stubby pump cone

  7. #7
    PWCToday.com Is My Home Away From Home Bionic racing's Avatar
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    Re: 550sx Coupling Damper Install Direction

    Those rubber damper get real hot , will steam up when water hits them when your riding , that's one reason to always have a splash guard in place

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