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OX 66 225 HP Overheating: Yamaha Techs?

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  • OX 66 225 HP Overheating: Yamaha Techs?

    This is for the V-6 225 from year 1998 Running time 300 hours.

    With engine in the water, and intakes below water level:

    It is overheating. Not a faulty alarm, the block is hot.

    Next thing, there is a GOOD STREAM OF WATER out of the tell tale ( or "pee hole" in the vernacular of where I fish )

    I replaced the water pump, and it works well. It brings up water from the intake up to the top of the engine. The old impeller was actually in very good shape. Still very supple, and no chunks missing out of it, small amt of wear on the blades. The blades are almost full thickness as they were when they were new.

    The water tube must be good, or else water would not be making it to the upper engine.

    Engine rpms are low. And it stalled out a couple of times while sitting at the dock.

    I'm thinking faulty poppet valve, and maybe faulty thermostats.

    I had the overheating problem before I changed out the impeller, and that was what prompted the new impeller. But apparently the overheating is caused by something other than the water pump because that pump is working fine.

    Would love to hear your opinions about where to look next. Thanks very much, gents.

  • #2
    You answered a good bit of it yourself. Pull the stats and poppit and see how they look. Test stats or just go ahead and replace. Hope they are not vintage '98 Use a flash light to examine the bores.

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    • #3
      PStephens: Bores have corrosion inside you can feel. Stats had some corrosion, but the spring is not corroded open / shut. You can move the spring. Didn't get to the poppet valve yet. What's the trick with the bores? Thanks for answering up. Jake

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      • #4
        You could test the stats but why bother. I would replace both to be on the safe side, around $30 apiece. Replace the pop-it too, fairly cheap as well. Corrosion inside the bore (water passage) varies between minor to horrible. One of the fellas on here (Fairdeal) had some pics of before/after on his F225. Did a nice job of halting the progression. Maybe you could post pics of your concerns and some of the members here can weigh in?

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        • #5
          Looks like $21.95 each for your thermostat on this site. Pop-it, spring and grommet prob less than $15.00

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