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  1. #1

    got something caught in impeller, need info

    This is my first year with a wave runner. I have a 2018 FXHO. This afternoon I was cruising along and the machine made that dreaded noise and it slowed right down. I knew I had something caught in the impeller. This has happened to me before but it only lasted for a short period of time, thankfully.

    This time not so lucky. I drove slowly back to the dock. When I got home I looked under and found a small piece of plastic in the impeller. I removed the grate and was able to remove the small piece of hard plastic.

    This is a dumb question but what is going on where this little piece of plastic causes the machine to make such a noise and not able to getup to speed? IS the impeller not able to rotate last enough? Was it ok to limp back to the dock or should have I got off immediately and tried to clear the issue in the water?

    Thanks in advance.


  2. #2
    Click avatar for tech links/info K447's Avatar
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    Debris caught in the jet pump causes cavitation. The impeller is spinning just as fast as it normally does, or even faster. The trapped debris pushes the water aside as it spins around, leaving a trail of bubbles.

    Not air bubbles, but vacuum bubbles. The individual bubbles quickly collapse but the overall effect is that the impeller blades are spinning in a mixture of water and vacuum.

    The impeller cannot efficiently compress the cavitated water to generate thrust, which is why the engine will rev up but there is not much forward motion.

    As you have discovered it doesn’t take much debris to significantly reduce thrust.

    Unless there is evidence of damage to the impeller, your watercraft is probably just fine.

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  4. #3
    Click avatar for tech links/info K447's Avatar
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    Tip: Experienced riders often carry a small collection of tools and such to extract debris from the jet pump. I carry really long forceps, a folding pruning saw, long fillet knife (in a hard sheath), and a few other things. A long metal rod with a hook in the end can be useful.

    For difficult extractions, the ski can be rolled onto one side in shallow water or near a beach. Two people can hold the machine sideways while a third works on removing the troublesome item.

    Tip: Always rotate the hull so that the exhaust side of the engine rolls downwards. For the Yamaha 1.8 liter engine that would be the hull left side down.

    There is water inside the waterbox, which can flow back into the engine if the hull is rolled such that the exhaust system is above the engine.

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  6. #4

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    But dang you are a wealth of knowledge. It seems like everyone who posts an issue hear gets an answer from you that is not only informative, but well thought out and intelligently written. You impress me sir.

  7. #5
    TimeBandit's Avatar
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    Quote Originally Posted by sys1mxb View Post
    ....
    Was it ok to limp back to the dock or should have I got off immediately and tried to clear the issue in the water?
    Thanks in advance.
    The only thing I'd like to add to the already great advice, is to be cognizant of the Yamaha open-loop coolant system during such times. If debris is cavitating/ventilating the thrust, depending on the severity, could also compromise the coolant flow. Is it safe to limp back to shore ?? As long as you see tells (small pissers) on the side of the hull still expelling water, I'd say it's fine to baby-it to the nearest shoreline. Another good indicator if the jet-pump is being productive, is to look at the water flag height, as this feature is powered by the same positive nozzle pump pressure that also pressurizes the coolant supply. Thus as rpms rise, if you notice the water-flag not very strong, you can equally deduce your coolant supply line is also not as strong.

  8. #6
    txgp1300r's Avatar
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    We have successfully cleared a fouled pump by backing one running ski up to the non running ski pump, opening to pump opening , then stab the throttle blowing thrust water into the fouled ski and dislodging the debris....

    this does not always work but sometimes it just does the trick and is worth a try.
    Last edited by K447; 09-06-2018 at 09:46 AM.

  9. #7
    Quote Originally Posted by K447 View Post
    Tip: Experienced riders often carry a small collection of tools and such to extract debris from the jet pump. I carry really long forceps, a folding pruning saw, long fillet knife (in a hard sheath), and a few other things. A long metal rod with a hook in the end can be useful.

    For difficult extractions, the ski can be rolled onto one side in shallow water or near a beach. Two people can hold the machine sideways while a third works on removing the troublesome item.

    Tip: Always rotate the hull so that the exhaust side of the engine rolls downwards. For the Yamaha 1.8 liter engine that would be the hull left side down.

    There is water inside the waterbox, which can flow back into the engine if the hull is rolled such that the exhaust system is above the engine.
    Thank you very much for the info. I will add those items to my wave runner.

  10. #8
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    I also keep a snorkel mask with me. I actually used it yesterday on someone's ski stuck in the middle of the river and cleared a water bottle cap stuck on their impeller.

  11. #9
    Click avatar for tech links/info K447's Avatar
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    Arrow Tips: Rolling your PWC over to clear debris from the jet pump

    Quote Originally Posted by xkon View Post
    ... someone's ski stuck in the middle of the river ...
    If you cannot clear the jet pump with it floating in the water and the shoreline is not accessible (rocky, steep, waves, whatever) it is possible to roll the ski completely upside down to gain better access to the jet pump inlet and impeller.

    Make sure the seat and hood are properly latched tight
    and there are no valuables in the glovebox or any other compartment that might get wet inside.

    Best situation is to have one or two other PWC (or a boat) nearby. Not only do they provide visibility to other boaters to stay clear, if the inverted ski floods or sinks you want to have a rescue option ready.

    Plan the work, collect the available tools. Tie a rope from the bow of the dead ski to a 'tow' ski, just in case.

    Ask any nearby skis to shut down their engines while they assist/wait. Less exhaust fumes, less noise. And less waves from 'bored' riders zooming off to play while you try to work.

    You do have a few minutes to work on the jet pump problem while the hull slowly* begins to fill with water.

    Tip: Always roll the hull so the exhaust system side of the engine rolls below the engine, to flip it upside down, then back to right side up.

    If you cannot clear the debris in a few minutes working time (and you suspect the hull is settling lower into the water), roll the hull back upright and run the electric bilge pump to clear any water that has leaked inside. This is another reason to have an electric bilge pump.

    * The factory configuration for the hull ventilation tubes has the hull fittings well above the waterline and the tube ends inside the hull are positioned down low in the hull. This is done specifically to prevent flooding the hull when the boat is upside down in the water.

    If somehow the ventilation tube ends have been moved from down 'low' in the hull to somewhere higher up, or one or more of those tubes have been removed/disconnected entirely, then the inverted hull can flood quickly.

    If additional 'ventilation' holes have been made in the upper deck, water can flood in fast when the hull is inverted.

    I recently helped a family with an older Seadoo 2-stroke. They rolled the ski to clear an ingested plastic bag, but they apparently rolled it over the wrong way, unwittingly sloshing water into the engine from the wet exhaust system. After righting the hull the engine would not crank due to water hydraulic lock in the cylinders.

    Eventually that ski ended up on my trailer for recovery efforts after a long tow to the nearest ramp. Full water geyser effect when cranked with spark plugs out. Eventually we got the engine to fire up and warm up. They rode it back home afterwards.

    Later on I heard it was not running quite right, which can happen after hydro locking. Possible internal engine damage. So, know which side to roll your ski onto

    If you suspect even the possibility that some water may have reached the engine, take the spark plugs out BEFORE you even 'try' to crank the engine. If no water comes out of the spark plug holes, put them back in and the engien is ready to start.

    If water does shoot out of even one cylinder, follow the recovery procedure for a water flooded engine.

    You do have a spark plug wrench on board, correct?
    Last edited by K447; 09-06-2018 at 02:27 PM.

  12. #10
    I would remove the prop and take a look at it. Not really hard to remove the prop.

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