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  1. #1
    Skijumper88
    Join Date
    May 2012
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    2011 ultra 300 - head scratcher

    Customers ski has been running fine. Suddenly it wouldn't much over 52-54. Changed plugs, no diff. Removed exhaust to check filter, it was missing and plugged the waterbox like a cork. Luckily, finally got that out and installed a new filter. I assumed this was the issue. Took it for a spin.
    Here's what happens - under easy acceleration from a stop, it hits 52-54. Boost is showing full. If I accelerate full throttle from a stop, get the rpms up quick from slight cavitation, she'll rip like it should up to 64/65 or so. Come to a stop, accelerate slowly...back to 52/54. Rpm around 68-7g. Back to a stop, full throttle out of the hole and speed and rpm back to where it belongs. Hoses tight, no water in hull, s.c. belt appears fine. No belt residue, feels tight and boost gauge is up. Compression fine, took fuel samples(couple cycles worth from inlet hose) and appers perfect. Scratching my head. Next I was going to run a fuel pressure check, unless something else solves this. Thanks.
    Last edited by jimfleming88; 11-03-2022 at 09:32 PM.

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  3. #2
    Myself's Avatar
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    May 2007
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    I had one last year acting similar. It had some water in the gas.

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  5. #3

    Join Date
    Jul 2019
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    Coppell, Texas
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    My 2011 is doing something similar. I have two identical machines. One is fine the other is the problem. The supercharger tensionser was frozen; fixed that, but didn't fix the probelm. Gas is clean (no water). Spark plugs gapped and clean. Fuel pressure is good. Going to check the exhaust filter next, but really don't think that is the problem. Did you ever find out what was going on with the one you were working on?

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  7. #4

    Join Date
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    Sweetwater
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    I'd agree that it doesn't make sense per the symptoms, but with these engines along with a compression test I do a leakdown. I've found the boost really beats on the rings a bit and you see odd issues.


  8. #5
    A bad speed sensor could do it.. ECU limits speed based on the sensor.

  9. #6
    For what it's worth, I also have two 2011 300 ultra LXs and most of the time it's spark plugs. This is especially true if the ski hasn't been ridden very much.

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