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  1. #1

    Intake Grate Cavitation

    I just installed a Riva Aquavein intake grate on my otherwise stock 2006 RXP. The first time I used it the lake was extremely choppy. Only about 1 to 1.5 foot, but lots of them. Very simillar to a closed course once the race starts. I was amazed at the cornering improvement under these conditions, it was awesome! My top end on the chop also seemed to be better. It really felt like the back of the boat was being sucked into the water!

    I did notice a high pitched whirl sound when I was zigzagging at slower speeds 20 to 30mph. I'm assuming this was cavitation. I also didn't seem to have as much jump from a standing start. Is this also cavitation?

    Does anyone know if this is common with the grate and whether or not that is cavitation? If it is, does anyone have a solution to fix it? Can it hurt the impeller? Etc?


  2. #2
    sourpower RXT's Avatar
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    check the prop & wear ring for damage

  3. #3
    Moderator Snoman's Avatar
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    Welcome to the forums!!!!The harmonics that you are hearing are associated with that grate..There is no harm to anything pertaining that noise you are hearing....Its just a noise it creates when in a turning position....It defiantly is not caveatting..If it was cavitating you would be on the gas,RPMs would climb fast and the ski would barley go noware..Also a capitation sound is more like a growling noise and not so much a humming or whooshing sound...

  4. #4

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    May not apply to your situation because I have a P-X but...

    Yeah it does it on my P-X... the whirl sound freaked me out at first too. Now I think it's kinda cool.

    I didn't notice any cavitation with the Riva. I have the pump shoe holes drilled too, which some people have stated "causes" cavitaiton but no cavitation for me.

    Now... when I installed the 15/22R, I noticed a "loss" of hole-shot, but I still don't cavitate but every once in awhile and only if I'm at a dead stop and go WOT. Then I get a "vwamp vwamp vwwaaaaaaaaaaaa" hitting the limiter once or twice at max, in less than a 1 second period of time. Again only sometimes off of a "dead dig->WOT" situation.

    Cavitation at the start feels like I'm "Spinning my tires" in a car and then they "grab" a second later and GO. Bouncing off of the rev limiter, hearing the pump gasping for water but only getting air and the boat not moving like it should. Like a loss of traction.

    Causes of cavitation can include:

    1.) Worn/Damaged wear ring
    2.) Damaged/bent prop or
    2b.) prop nosecone seperated from prop and moving up the driveshaft (can lead to #7)
    3.) Pump not seated into pump shoe correctly (debris in the way or pump seal damaged/worn or pump just not torqued correctly).
    4.) Improperly sealed pump shoe to ride plate/damaged pump shoe
    5.) Improper seal where intake grate meets pump shoe (or so I have read)
    6.) Damaged "fins" in the pump shoe (right in front of the prop). If there's any damage at all it'll cause cavitation. If they're damaged, just cut them out and smooth them down to nothing. They're fine either 100% intact or 100% removed, but nothing in between.
    7.) Damaged/worn Carbon Seal (thru-hull seal for driveshaft, would cause MAJOR cavitation even at speed sometimes)

    OR something as simple as;
    8.) Weeds/plant life in intake grate/pump area (happens to me once in a while).

    I don't know how the intake grate on an RXP differs from a P-X, but if the new grate has a smaller opening than your previous grate it can cause cavitation out of the hole due to not as much water being available to the pump at low speeds (like less than 10-15mph). The R&D grate for the RXP-X has this issue a little, and seems to be more prevelant on skis that make more power and have a taller prop therefore able to process more water from a start.

    OK enough typing... lets see what other questions (or corrections) come up.

    -=Mike
    Last edited by Mikey G.; 09-04-2008 at 01:14 PM.

  5. #5
    Thanks for the response snowman. The sound is definitely pretty cool. I'm glad to hear its not cavitation. I'm still getting a little cavitation on the start, but that sounds like its normal. My next upgrades are going to be the ride plate and impeller. But I have to see if I can do those and still race stock.

  6. #6
    Moderator Snoman's Avatar
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    Quote Originally Posted by rxpwfo View Post
    Thanks for the response snowman. The sound is definitely pretty cool. I'm glad to hear its not cavitation. I'm still getting a little cavitation on the start, but that sounds like its normal. My next upgrades are going to be the ride plate and impeller. But I have to see if I can do those and still race stock.

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