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  1. #1

    Help with missing at high RPMs

    I have a new to me last fall 2004 RX 12 that I just brought out of storage. Fired her up on hose and started and idled fine. When opening the throttle, engine would rev and run smooth to 6K RPM and then start misfiring thereafter and would not rev beyond 7K RPM. I removed and cleaned (but did not replace) all four plugs with no improvement.

    I did note that the waste gate actuator did not open at high RPM. I have not yet done Nitro's waste gate solenoid test, but will tomorrow. Could this be the problem? Ski was winterized as per the service manual instructions, but I do not remember doing anything specific for the waste gate solenoid which I now understand has a propensity to rust up and fail. Will also attempt to disassemble and clean/lube the WGS per Nitros thread if it fails the blow job test.

    Any suggestions would be greatly appreciated. Thanks in advance!!!


  2. #2
    JRINJAX's Avatar
    Join Date
    Oct 2007
    Jax, Florida
    Put a new set of plugs in it. They are $11 each at Advanced auto parts. The turbos only turn 6200-6400 the non turbos turn 7K+.

  3. #3
    I build Horsepower
    NitroShark's Avatar
    Join Date
    Jan 2006
    If your R12x pulls 6180 +- 50RPM in the water then it is normal and you have no problem. Top speed 61-62 GPS

    Rev limiter kicks in at 65-6600 RPM


  4. #4
    Thanks Gents.

    I have little accumulated experience with this machine and was expecting a higher top end RPM based on the engine performance in my Yamaha SX 230 HO boat. A trip on the water after I sent the post seemed to indicate no problems under actual load. But I will be changing plugs (on order) and oil/filter as a matter of routine annual maintenance anyway.

    Thanks for the prompt responses and education. You guys and this forum are a great resource. Keep up the great work!


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