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  1. #1

    Ultra 150 loss of power

    Hi Guys...

    I have an '01 Ultra 150, had the engine professionally rebuilt (non sbt) oem Kawi parts. Ran 50:1 first tank out, 100:1 second tank, regular pump gas no premix third and on...I was told that it MAY foul the plugs eventually. So about 9 hours on the new engine I was pulling into the ramp after a good day, and feel a loss of power (30-35MPH around) Idles just fine, figure it's the plugs. I remove them and replace with all 3 new.

    Today I took the ski out, first time with the brand new plugs. Was running great for the first hour, then all of a sudden, I feel a hesitation, loss of top end power.


    Idles OK, about 500RMP less than it should, but sounds OK.
    Struggles to get on plane
    Acceleration is good, but I can tell it is not 100%
    As soon as the ski gets to about 25-30MPH, it's running around 5k RPM and starts to sputter will not go much faster, and if you try, RPM will shoot through the roof. example 35-40MPH at 7k RPM is not right at all...
    First plug was wet (not water) but wet gas/oil (sticky around the threads)
    Compression test approx 115 #1cyl, 125 #2cyl, 125 #3cyl
    All 3 plugs were in good working condition and all checked for spark.

    Any ideas? Could something be wrong with the pump? Cooling system? I don't want to run it until I figure out what the problem could be.


  2. #2
    Did you do a compression test before this happened to see what you were getting? Your down 10psi in one cylinder was it that way before?

    Have you tried new plug again, you would be the first to foul them out back to back?

    I would pull the pump and inspect it for damage or bad bearings before I pulled any engine parts. If you don't find anything then I might pull a head off the low cylinder to see if its seizing.

    The "35mph=7000rpm" sounds like a pump issue.

  3. #3
    btldigger's Avatar
    Join Date
    Feb 2007
    lebanon tn.
    You may have 2 problems. There may be something stuck in the pump. And it has fouled the plugs again. I have had to run br8es plugs on some setups because of fouling at idle. Something does sound up with that #1 cylinder being down 10psi.

  4. #4
    Shogun: I did not do a compression test on the stock engine before the problem. Do you know what the spec is? I have the shop manual, it might be listed...

    btldigger: I know you're very familiar with the ultra 150, could you explain some more? I'm in the process of taking the pump off the machine to inspect, what would you think could be wrong with the #1cyl?

    I hope it's not a broken ring or something that will destroy the cases. The problem happened and I had to ride the machine back to shore for about a half hour 30MPH 5k RPM, and then Idle speed (No wake) <5MPH 1-2k RPM

  5. #5
    I just took apart the impeller housing, here are some pics. Two are of the impeller itself, you can see that it is damaged. The other is of the housing, you can see that there is sand damage, as well as some 'waves' in the metal.

    While I was in the water I put my hand near the 'cone' on the very edge of the impeller in the nozzle. (while it was off of course!) and it felt warm through the water...

    Not sure if this could cause the above symptoms...
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  6. #6

    Join Date
    Sep 2008
    Can you feel any roughness while rotating the impeller with your hand? Check that while u have pump assy off unit.

  7. #7

    Join Date
    Sep 2008
    Don't freak just yet about 10psi. Service manual spec is 98-155psi
    Last edited by bamatech; 09-14-2008 at 02:54 PM.

  8. #8
    I'll check, how can this be done? Just by spinning it?

  9. #9

    Join Date
    Sep 2008
    With jet vane housing off unit and impeller still in it, rotate the impeller by hand. If you feel roughness/grind or stiffness the bearing is failing. NGK BR9ES is correct plug for your unit also.

  10. #10
    No noticable grinding or roughness. It spins well. When I ran the ski out of water to get the excess water out of the engine, after the machine was shut off, you could hear the impeller spin for a few rotations after the engine was off. Now, I really didn't hear any additional revolutions. However it still seems like it spins freely.

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