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  1. #1

    What happens if I ride with a worn impeller?

    Hello everyone,
    As I mentioned in my "I'm afraid of the Supercharger" thread, I picked up a used 06 FX HO that has too much clearance between the blades and the impeller duct housing. If given full throttle at a dead stop, the machine barely moves. Let off the throttle, throttle up a little slower (think 2 seconds from dead stop to full throttle) and the ski moves right along. Three (maybe four) questions for the community:

    1 - How bad is it to run the waverunner with a worn prop? Will I do other damage to the housing?

    2 - How hard is it (really) to get the prop off an 8 yr old machine that has been ridden in salt water? I've seen other threads with home made tools to get props off, are they all that tough?
    2a - At what price point would you let the dealer do it? I live in South Florida, so I'd take it to Riva.

    3 - I see an OEM prop is $290 (list) and Solas DynaFly 14/20 is $218. I don't plan to mod the waverunner (maybe velocity stacks, but that's it), any recommendations from the group? Other parts suggested/needed for this? I see different kits to fill and smooth the water flow from intake grate to the housing. Are these needed? Helpful?

    Thanks for the discussion!

  2. #2

    Join Date
    May 2005
    plenty of used cheap impellers out there - Riva probably has many - check with them - Let them know your on a budget. Good luck - you can at least take the pump off. - nothing too hard.

  3. #3
    Mighty Mouse's Avatar
    Join Date
    Feb 2011
    IMO, it wont hurt anything, but it'll be discouraging if you ride with others. In addition, it'll be worse when you ride 2 up. It will also be totally impossible to pull any tubes, skiers.

    As far as how hard it would be to remove impeller: Some are harder than others, but never found one I couldn't remove. You'll need a impeller tool to remove. Often times they are lock tighted on and you'll end up using a cheater bar on it. Personally I wouldn't take it to a dealer. It's not that bad of job. You have a chance to look at the pump if you want while it is off.

    I've found that after market impellers are often better and most defiantly cheaper that OEM. I like Solas, but I am sure others will have different opinions.

    Finally, are you sure it is a impeller issue? Often time it is the wear ring. It should have a SS wear ring, but may have been changed to ABS which are replaceable. The only way to know is to pull the pump and have a look see.

  4. #4
    Thanks for the responses, I do not know if it is the prop or ring, but I can clearly see a gap well over the 0.6mm outlined in the manual. Showed my son the difference between the two props, on the FX base, can just barely see a gap between impeller and housing (when looking from the rear of the machine) to a gap the thickness of a credit card on the HO. I will start to take it apart to see.

    Once apart, how would I know if I have a worn prop or worn housing?

    Thanks again,

  5. #5
    I like pipes. I love boost Mr. GP1800's Avatar
    Join Date
    Jun 2010
    Milwaukee WI
    I would think the wear in the housing would be pretty apparent. If it were me, I would send the props off to be refurbished, and reinstall them. If the gap is still out of tolerance, then replace the wear ring. If your wear ring is stainless then its most likely the prop that is worn.

  6. #6
    Hello everyone, I can now answer my own question...

    I started to take the prop out to have a look. Got the rear ride plate bolts off, no problem, could not get the bolts that hold the pump ass'y together, and could not get enough clearance to start working on the lower bolts. Tried to heat them, used PB blaster, let it sit overnight, etc. Then decided this is the point where things can really go wrong, so just took it to Riva. At first glance, the service writer said "wow, you have wayyyy more than 1mm clearance there!" Spec is 0.6mm clearance. Below is a pic taken on my workbench after replacement (I didn't take a pic as it was installed in the machine, but you get the idea):

    Click image for larger version. 

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    To give some scale, here's another one... yes, that's a penny on top of the prop...
    Click image for larger version. 

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    I actually bought feeler gauges before I realized just how worn the prop was, total gap was just short of 2mm. Now in the pics the prop is obviously not centered, so it would have read a little less than 1mm on the machine. Still, at this point, she was hitting 55mph, on gps, on flat water with 220lb rider. I am really optimistic when I get it all back together and test it out, I should have a very reliable, fun machine.

    To continue the story, I got a call from Riva about an hour after dropping it off, yup, I needed a new wear ring as well. I suspected that, but was hoping I could get away with just the prop. You can see the wear in this pic:
    Click image for larger version. 

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    Click image for larger version. 

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    At the bottom of the pic, you can see the straight machined lines of what the wear ring is supposed to look like. The "rough" looking material is where the prop sits in the ring, and between the cavitation and the sand (waverunner was used predominantly in the Keys and West Coast, Florida) the ring was worn enough to feel a diameter change.

    Also, as this was a salt water ski, there can be corrosion between the stainless steel liner and the aluminum housing. This corrosion behind the liner will force the ring to be slightly out of round, and also wear the prop. So you can't just fit a new prop and accept "a little" cavitation, as you will end up right back where you were (worn prop, faster wearing liner) pretty quickly. You can see the corrosion, and resultant high spot here at the top of this pic:

    Click image for larger version. 

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    So, what I thought would be a (admittedly not so quick) $200 prop replacement, quickly escalated to a $700+ Saturday. Riva did give a little discount on the prop and ring, and the hour and a half of labor they charged to take apart a salt water ski and assemble it correctly, the first time, with all the right sealants, etc., I thought was pretty reasonable.

    So, my advice to others would be: If you notice the cavitation, get the prop replaced quickly enough and you may save your liner. The flip side of this is if you are paying labor to take the prop out, it doesn't cost any more to replace the liner, so try to look on the bright side of whichever situation you have!

    Good luck and happy riding!

  7. #7
    64physhy's Avatar
    Join Date
    Aug 2010
    Weatherford, TX
    If it was in the Keys, the previous owner probably beached it a lot, and sucked a lot of sand through it and eroded both the liner and the impeller.

  8. #8
    Like a chimp with a ball-peen hammer smackwave's Avatar
    Join Date
    Dec 2005
    Annapolis, MD
    Glad it worked out well, that's a shocking amount of gap. The last time I saw something like that the pump bearings had gone bad, but Riva would've spotted that in a heartbeat so I'm thinking you're good (it's possible the previous owner had the bearings replaced and sold the ski when there was still a cavitation issue). Regardless, in response to your original question #1, there's two problems that can be caused by running a worn prop beyond the poor performance caused by the cavitation - since you're pushing foam and not water into the cooling system you're much more likely to cause an overheat, and all that cavitation will eventually erode the stator vanes which will cause a minor loss of performance.

    Anyway, good job getting it taken care of instead of just riding it out and possibly causing further damage. Hope you get lots of good use out of the ski!

  9. #9
    Quote Originally Posted by 64physhy View Post
    If it was in the Keys, the previous owner probably beached it a lot, and sucked a lot of sand through it and eroded both the liner and the impeller.

    Youd be surprised, there are only a few "sandy beaches" in the keys, Most places even are just crushed up coral. We do have various types of bottom, and its all shallow, but most of its not real sandy. Lots of muddy areas in the turtle grass beds. Ive puled chunks of coral out of intake grates. To be fair, ive pulled a lot of random things out of intake grates here.

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