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Ox66 225 2002 Power loss (Fuel?)

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  • Ox66 225 2002 Power loss (Fuel?)

    Hello, i have a 225 HP ox 66 2002 that looses power around 3500 RPM (educated quess, based on speed, the tach does not work). When the throttle is about half way and im doing around 45 knots the engine seems to run out of power and if i dont move the throttle for 20-60 seconds the engine throttles down and comes back to full speed in about 10 seconds.

    As far as i can read, its most likely a fuel problem. I have cleaned the VST filter, which was very dirty, and i tried removing the low pressure pumps to see if they were leaking. When i unscrewed them and squeezed the bulb they all started leaking from the gasket marked nr 43, 42 on the link below. But they did not leak when they were screwed to the engine. And this is where im stumped, on the link below it shows a gasked between the pump and the engine block, marked 52. But this gasket is not on any of the 3 pumps on my engine.

    Could these missing gaskets resoult in pressure loss enough to stall the engine ?

    I will replace the gaskets and pumps of course, but i am just wondering if this will fix my issue or should i check somethings else before i order new parts ?

    btw, i also tried bypassing all the 3 pumps using a simple electric fuelpump that gives 4 psi and 120l/h. This ofcourse made the problem worse, loosing power at about 35 knots instead. What psi does the low pressure pumps feed the high pressure pump with ? '

    The engine also uses a ridiculous amount of fuel

    Martin Lund

  • #2
    link ; 2002 VX225TLRA Yamaha Outboard FUEL 1 Diagram and Parts


    • #3
      If the low pressure pumps are more than a couple years old, I'd replace em anyway. They have become a maintenance item rather than a check them to see if they work item. I also think it's a fuel problem as most OX66 issues are. Check rail pressure. It should be around 35 psi. You could also run it on an aux. tank to eliminate anything before that. Next check and clean the O2 sensor.


      • #4
        I have tested an aux tank, i just need to get hands on some equipment to meassure the fuel pressure


        • #5
          Keep us posted. We always like to here whether it's fixed or not.