Results 1 to 7 of 7
  1. #1
    Member
    Join Date
    Sep 2015
    Location
    alabama
    Posts
    3

    2001 200hp ox66 won't reach max speed

    Been having trouble with motor not reaching max speed. Usually at 5900 RPMs i will be running 64-65. Now motor will get up on plane good and run good up to around 50-55 MPH and just stay there. It is inconsistent but usually after 5 min or so it will "pick up" and run wide open. Some times it will never pick up. I have had the low pressure pumps replaced, soaked and cleaned 02 sensor, brand new set of NGK plugs and cleaned the filter in the VST. Tired of throwing money at it with no solution. Any suggestions are appreciated.

  2. Member
    Join Date
    Oct 2004
    Location
    Lake Charles, Louisiana
    Posts
    3,413
    #2
    Sounds like 02 sensor...I never cleaned mine just replaced it..

  3. Member
    Join Date
    Dec 2004
    Location
    Conway, AR
    Posts
    1,070
    #3
    I had similar issues and replaced O2 Sensor, even though it tested good. My problems stopped when I did.

  4. Member
    Join Date
    Sep 2014
    Location
    Dallas, TX
    Posts
    1,104
    #4
    When you cleaned the O2 sensor, did you pull the plate and clean the tube too? If not, chances it is clogged with carbon and cleaning just the sensor didn't work as expected.

  5. Member
    Join Date
    Sep 2015
    Location
    alabama
    Posts
    3
    #5
    soaked them both in Mercury Power Tune overnight. Very little carbon dust on the tube when I first removed it.

  6. Member
    Join Date
    Sep 2014
    Location
    Dallas, TX
    Posts
    1,104
    #6
    The things you did were maintenance items, so it's not lost money. The VST filter is very fine, so just cleaning it may or may not work depending on the condition. There is a test procedure for the O2 sensor that involves heating it with a propane torch. Send me a PM, and I will look it up for you. Could be fuel lines breaking down. Have you replaced the fuel filter on the engine? Any trash there.

    Once it picks up, does it go back down or stay WOT? If it stays, I would be looking for fuel restrictions. If it jumps back and forth, I would test the O2 sensor. That's not something you want to replace for fun.

  7. Member
    Join Date
    Jul 2014
    Location
    Chesterfield VA
    Posts
    3,402
    #7
    I wonder if the O2 sensor test could be done with a heat gun? I can't recall what temp you have to get it up to, but a torch could easily get it too hot. Just thinking there may some degree of safety factor in using a heat gun, if it can get it hot enough in the first place.
    Kevin | 2000 Champion 19​1 | 2000 Yamaha OX66 200hp

Tags for this Thread