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  1. #1
    snowrunner's Avatar
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    Unhappy Low RPM 7700 and Top Speed 70 with S3 and C5 SC's on 04 RXP

    Having some problems with my RXP. Thought it was just my wear ring, so replaced it and my prop this year.

    Was able to muster 74 (didn't look at revs cause I saw my ring was damaged) with my S3 SC and 15/20 -2mm on trailing edges (81mm nozzle).

    This year went to the R&D C5 Monster + an un-touched 15/20 + RUDE RRFPR, replaced plastic ring with SS wear ring. Wasn't watching revs or speed went was beaten by a stock RXT. SO, looked at tach 7650-7700 at 70 MPH. Running 81mm Nozzle. Fuel pressure at WOT was 58 psi, baseline was 61. Slip on the SC was 110 in-lb 1 hr ago. Oil was near the add mark on the stick, need to do an oil change and know of the potential to run lower RPM due to low oil.

    Also, getting a shudder or wobble feeling in the seat at low and mid range speeds. Getting water in the hull while riding relatively flat water, possible carbon seal causing the problem, also found water leaking from yellow fitting on siphon tubes? Front mount seems ok, but how do I hknow if it's bad other than trying to rock the engine in the engine bay?


  2. #2
    dduck dduck1628's Avatar
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    Do you have anyway of checking boost pressure? Mainly to verify that you don't have any boost leaks. Check your plumbing for that water leak too. I chased one for a couple of days before finding a pin hole leak on one of the hoses going to the XS, it only leaked at WOT.

  3. #3
    Carbon seal or broken motor mount? Probably the carbon seal.

  4. #4
    snowrunner's Avatar
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    how are people checking for boost leaks? Only way I can guess to do it is to tie the ski to the dock and snoop (soap and water) check.

    Any idea on the wobble? had this with the S3 setup, before I got your old C5. Lost on that one.

    Eric
    Last edited by snowrunner; 06-15-2009 at 08:10 PM. Reason: No one offered a dick to use so a dock might work better

  5. #5
    dduck dduck1628's Avatar
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    I use this stuff and A/C repair guy gave me, said it doesn't cause metal to corrode like dish soap. Wet boost tubes & hoses down and snapped throttle a few times and look for bubbles foaming up. I was missing 2 lbs of boost and 3 mph cause of a couple of clamps that needed to be tighten with my current setup. It was easy to pick up on with the boost gauge. I've since switch to constant torque clamps, (they are spring loaded).

    I'm having a hard time visualizing how that wobble must feel? Does it do it out of the water? Does it seem like the engine is surging?

  6. #6
    snowrunner's Avatar
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    Almost feel like an im-balance in the driveline. Doesn't really feel like surging, almost like a miss. Was curious if I'm running on 3 cyls, sounds like it from the exhaust note but not able to get turn the prop like you did.

    I beleive you were running an 81, the 15/20R and C5 in salt water - is that correct? I'm running 73F lake temp, freshwater. I have my old 15/20 with -2mm.

    Went thru and re-torqued all band clamps, no change in RPM.

  7. #7
    dduck dduck1628's Avatar
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    I was running 76-77 @ 8120rpm in the FL summer heat and humidity with that setup. Check your coils for cracks on the sides while you have the plugs out.

  8. #8
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    Slip should be at 140-150 wet...you need it higher.

  9. #9
    paulthepwner's Avatar
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    Quote Originally Posted by snowrunner View Post
    Only way I can guess to do it is to tie the ski to the dick and snoop (soap and water) check.
    that's gunna hurt

  10. #10

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    If you don't have a boost leak or any other major problem. Try and 83 ring and see what your RPM's do.. Could just be too much prop?

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