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1987 Yamaha Pro V 150 losing power after it warms up

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  • 1987 Yamaha Pro V 150 losing power after it warms up

    I purchased a 1996 Stratos 285 XL with a 1987 Yamaha Pro V 150. This had been running good until just recently. When I first put the boat in the water and fire it up, it works well. It fires up quickly and runs smooth. The first hole shot is very good. As the engine runs and heats up it starts losing power. Any subsequent hole shot is non-existent. I usually have to get a buddy to move to the bow to get the boat to level out and then it will get up some speed. But this still does not get to full speed. The initial hole shot gets to about 5000 RPMs and running down the lake will reach about 5500 RPMs. Afterwards the hole shot will only get about 3500 RPMs and running down the lake is about 4500 - 5000 RPMs. I have replaced the coils with new ones and replaced the spark plugs. Still the same issue. I have checked the cold compression and see a level of 100-105 for all the cylinders. After it warms up I get a compression level of 95-100. I checked the spark with the plugs and see a weaker spark than I normally do with other engines. The engine seems to be running smooth without any misfires or sputtering. Has anyone experienced this or know where I may look next? Any assistance is appreciated.

  • #2
    make sure timing is advancing as it should and fuel pressure is staying good when the problem shows up

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    • #3
      I would check the stator charge coil outputs once warm.
      but that is just me.

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      • #4
        Thanks for the suggestions. I know what I will be working on this weekend.

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