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  • Throttle postion sensor may be bad?

    Hey Guys. First and foremost I wish to commend everyone on this site. I have gained a wealth of information and saved hundreds of dollars. For that I thank you.. ( Tipping of Hat).

    I've been toying with my 2001 Yami ox66 250 for a while now and trying to understand why I can't reach over 5000 RPM, I understand WOT should be around around 5500. My first thought was the prop, so I called Edgewater and asked a silly question. "What should the proper prop be on a 2001 225 CC with a Yami 250. The response was a 19 pitch. or 19M which is stamped on the hub. The diameter I think is 17, but I'm 100% sure. So the prop appears to check out. I remember someone having a similar boat and setup, only he was able to reach 5600, and 48 MPH. NICE!!!!!

    Anyway, after going through the service manual about 4 times, and the chelmer service manual I decided to look closer at the TPS. I followed the steps by first disconnecting the linkage on the #1 throttle body, and check the voltage between the orange and pink wires. The voltage was reading low so I made the adjustment to read .5 volts - 5 volts. Only my DVM at WOT was reading 4 volts. So could this sensor being going bad bacause of the voltage drop of one full volt, and could this be the reason why I can't reach top RPM? The sensor is not cheap so I need to exercise caution when replacing expensive parts.

    In addition, I have adjusted the oil link to spec. Cleaned the O2 sensor, cleaned the VST filter, fuel filter, water sep filter, and replaced the plugs. Of course all of this items were addressed throughout the summer. The only other three items I'm have not ruled out are the pumps, replacing the O2, and TPS sensor.

    Commpresson check fine...

    She runs fine, and even better once I adjusted the oil link and TPS. As before she would run rough and hesitate a litter out of the hole. So I may be onto something with this I sensor I believe.

    Any ideas?

    James

    Stuart, FL
    Last edited by jperconte; 08-19-2010, 07:23 PM.

  • #2
    TPS reading of 4 volts at wot is about right. Might check timing at wot to see if is about what it should be.
    Regards
    Boats.net
    Yamaha Outboard Parts

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    • #3
      Originally posted by boats.net View Post
      TPS reading of 4 volts at wot is about right. Might check timing at wot to see if is about what it should be.
      Timing is con*****ed by the ecu on this engine. I did not see any adjustments in the manual. I'm I missing something here regarding timing?

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      • #4
        There is not an adjustment but if timing is off then may be due to sensors on engine that send data to ECU.
        Regards
        Boats.net
        Yamaha Outboard Parts

        Comment


        • #5
          Id try borrowing a 17 pitch or less, and see if it goes up in rpm. Ya never know. if it goes up to say 5500, then i would think your tps is good.

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