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Z150 HPDI down to 3 cylinders

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  • Z150 HPDI down to 3 cylinders

    Thank You in advance for any and all help.

    I have seen this issue listed on the foums but could not find any that posted a resolution.

    I have repowered an old boat I purchased with a 2000 hpdi 150. It sat for about a year i believe. I have replaced the the trim unit which was why the guy was selling it. I now have it mounted on my aluminum 18ft starcraft.

    It starts right up with a small bump of the key, it has a small lag on acceleration and then hits a max of 12mph, and around 1500 rpms.

    I replaced the fuel supply hoses and the primer bulb, there is no air coming in there. I have not made it to the VST yet. I was checking the plugs, there is no shavings on them, they were covered in gas and a little carbon. Yet when I pulled the wires, there was no change on 3 of the cylinders???

    Near as I can tell 2 cylinders on one side the top and bottom, and the one in the middle on the other are not functioning at all.

    I understand it idles on 4 cylinders but I am missing 3, could this be caused by the VST?

    If not what else could cause it, the fuel supply appears constant with no interruption in flow (the ball stays hard).

    If the VST is a problem would it still start right up with no hesitation and no priming. It does not die, or surge there is just no power.

    Primarily I have dealt with I/O's with carbs, this is my first outboard, I was hell bent on finding a yamaha but now I am not sure where to go from here.

    Thank You,

  • #2
    A motor sitting that long probably need the VST and all filter and screens cleaned/replaced

    Need to see what the fuel pressures are, that will guide you if there are restrictions and where they are. Injectors also may need to be sent off to have flow tested and cleaned.
    Lots of stuff to be looked at on those motors , a computer hooked up will help you eliminate a lot of things quickly