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  1. #1
    Speed Junkie UnleashedBeast's Avatar
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    2015 310X SE - Low Boost, RPM, & Speed (1st post updated)

    I'm pulling my hair out trying to get back the performance I had when the ski was new. With simple mods, it was a 70-72 mph @ 7900 RPM ski. *Depending on temps* However, now it will not do better than 64-65 mph @ 7480-7600 rpm *depending on temps*. Boost shows 11 PSI on the instrument cluster. It used to hit 15 PSI and scream. Now, it can't even get to the factory speed limiter like it did when it was new. My modded ski is no faster than a 100% stock Ultra 310 (tested May 2016).

    80 hours on ski

    Here is what I have done to troubleshoot the problem (as of May 16th, 2016)


    • Removed and cleaned the intercooler 3 times and both large 4" hoses - also resealed the sides of the intercooler with better gasket maker (Right Stuff)
    • Pressure tested intercooler and hoses @ 20 PSI. Nothing leaks except small seeping from wastegate. (now removed and blocked off)
    • Compression test yields 150 PSI in all cylinders
    • Leak down test is less than 3% is all cylinders
    • Replaced spark plugs twice with NGK 3521 CR9EIX
    • The engine cooling system seemed to be clogged (pisser was weak). I cleared that (no change)
    • Disassembled, greased, and reinstalled belt tensioner. Some evidence of belt dust, but that is common on PD blowers.
    • Impeller looks fine, no damage seen from either side. Impeller to pump tunnel clearance is .008 (well within tolerance)
    • Replaced the BOV with a known working valve (Thanks Mike H)
    • Checked pump bearings for wear and play. No problem found
    • Replaced the exhaust filter. Old filter was suitable for continued use, but since I had already bought a new part, I installed it anyway.
    • Tested fuel output at ECU power up (3/4 cup - 175 ml) perfect flow
    • Supercharger isn't making strange noises, but have found small metal pieces in the intercooler.
    • Verified throttle body is opening 100% when lever is pulled to the grip. Throttle cable is hitting the stop.
    • Replaced the ECU with a brand new one from another 2015 310X SE Jet Ski. Also tried a reflashed ECU from K-Speed. (no change)
    • Verified that all 6 bolts connecting the supercharger output duct to the bottom of the supercharger were not backing out or causing a leak. Pressure tested OK.
    • Inspected the throttle body rubber isolation mount. Looks brand new, had no cracks, or separation from the metal base. No leaks when tested under pressure at 20 PSI.
    • Install RIVA air intake with more hull air mods. Air vent added to opposite side of hull of gas fuller neck. Tubes removed from all other vents.

    As you can see here, this is how I pressure test everything in the air pathway to check for leaks.



    It was fine last summer, but then.....it's like something "flipped a switch". The craft lost boost instantly (not a slow degrade), it no longer had that "rip your shoulders out of your sockets" launch anymore, and would not achieve the speeds it once did. You can tell it's "lame" from a stop, and no longer has the acceleration it once did.

    Here are speed tests both before and after the "instant" change.



    This was a picture taken during the August 15th, 2015 speed test at wide open throttle on the river.



    I am open to all suggestions, but the only thing remaining is for me to remove the impeller, looking for any damage I am unable to see and if the pitch is correct.
    Last edited by UnleashedBeast; 07-08-2016 at 11:37 AM.


  2. #2
    nicjak's Avatar
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    for one thing thats not how you check the belt tensioner why did you split the i/c? that could be your very issue!! well the exhaust filter should be first on the list to check given there are no difinetive hrs they last. boost is also governed by rpms so no rpms no boost

  3. #3
    Speed Junkie UnleashedBeast's Avatar
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    Do BOV's fail on this ski? How do I test it for leaks?

    Quote Originally Posted by nicjak View Post
    for one thing thats not how you check the belt tensioner
    Is there a link of how to do it properly? The belt is tight by touch. I thought it could have been a belt slip issue, so this is one of the first things I checked. A "how to" diagnosis would be great.

    Quote Originally Posted by nicjak View Post
    why did you split the i/c? that could be your very issue!!
    Symptoms are the exact same before and after intercooler cleaning and end cap resealing. No change. I was able to clean out a few metal chips I found in there, likely came from the supercharger. I also found heavy dark gray greasy deposits in the orange 4" hose which connects the supercharger to the intercooler. I cleaned that out the best I could. In fact, if I can judge by the instrument cluster boost guage, I gained .5 PSI of boost (half bar) after resealing it.

    Quote Originally Posted by nicjak View Post
    well the exhaust filter should be first on the list to check given there are no difinetive hrs they last. boost is also governed by rpms so no rpms no boost
    I will check that tomorrow morning, or tonight if I have time. I didn't make checking the exhaust filter priority because I didn't think it would keep the engine from making more than 7500 rpm.
    Last edited by UnleashedBeast; 08-15-2015 at 04:03 PM.

  4. #4
    Mines doing the exact same thing. My mods are

    2 degree pump wedge.
    deep fuel extender.
    block off plate.
    ecu tune.

    Hasn't ran right for a while. Got it all serviced and checked also.

    It came back all good. Pending they didn't take it for a test run. It should be pulling 8000rpm @ 117kph on gps.

    But getting 103kph and 7500 rpm. And at wot off take off no jump to 8000rpm just builds up to 7500rpm. Running 10-11psi. I'm lost.
    ��

  5. #5
    Speed Junkie UnleashedBeast's Avatar
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    Everything was fine, until one day on the river. One minute, it's running 70ish @ 7900 rpm. The next, 64 @ 7500 rpm. I wonder if this is the same problem some 2014 ECUs had?

  6. #6
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    My tensioner was good untill all the sudden it wasnt. It had lost all the oil out of it. Belts still "simi" tight as the spring has tension on it but it doesnt work right without oil in it. Put that 19mm and a breaker bar on the tensioner assembly. First time you move it up (like you're trying to give the belt slack) it should be fairly hard to move. Work it a few times up and down, should get harder each time you try to move the idler up. Try that and make sure the pivot is greased

  7. #7
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    A broke, almost broke exhaust filter will absolutely choke things up and slow you down too

  8. #8
    Speed Junkie UnleashedBeast's Avatar
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    Thanks Mike H, I will check the tensioner for proper lubrication. Anyone done a good write up on this?

  9. #9
    nicjak's Avatar
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    Mate you need to remove the tensioner to check it. Ive wrote of this explaining several times here.
    Once the tensioner is removed split a washer off the pivot point push out the bushing clean the outer surfaces grease it and reassemble. Most think it pivots on the pin it doesnt. It has an enclosed bush

  10. #10
    Speed Junkie UnleashedBeast's Avatar
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    Got home, disassembled the exhaust filter area. While it's some signs of wear inside the large middle hole, the rest of the honeycomb is in perfect shape. No clog here. If the dealer has one in stock, I will go ahead and replace it.

    Will check the belt tensioner better while it's apart.

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