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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    I know that's why changed ot
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    MAP sensor is new and compared redings in Diacom with gauge connected to intake manifold. It works well. Its on Bayliner VR5. Bought it with 14.25x21 and now 14.5x19 is installed. With this setup it should rev to 5000-5200.
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    Because of low vacuum on idle. If its low on idle and its probably wrong throughout the rpm range. PCM control's throttle and timing. I will try to get graphs next time on water. There are no knock sensors on that engine. Found something interesting but that general info for ecm555. Injection...
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    New boat to me that's correct. See serial number on attached picture
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    Called arbitrated because that's probably average of two throttle sensors (TPS1 and 2 counts) but it general its percentage of throttle opening. It is drive by wire. I thought what whatever value of demand is should be achieved. Looks like engine is struggling to breath and PCM is doing...
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    That vacuum line from fuel supply module was first i checked. No fuel. Tried to suck on that hose and seems that pressure regulator holds well. Can I leave it of for test on water plugging intake manifold side? Maybe under load it does something different. It's no catalyst version. Also checked...
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    It does but too much imo. Vacuum is not shown directly. Vacuum is a difference between barometric pressure and manifold pressure. At WOT they both read nearly the same as you would expect but it's very low at 3000rpm when throttle demand is at 58.2% but arbitratted throttle position only 21.4.%...
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    Fuel pressure steady at 45psi - checked under load while on plane.
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    What do you mean wrong way? TMAP it's integrated MAP with temperature sensor. New sensor readings in Diacom verified with gauge and shows the same. Needle steady at 12inHg on idle. But should be 17-22 not 12. Checked throttle body works full range to 90deg.
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    It was during startup. If diacom connected after warmup no misfires.
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    No and tried two different props didn't see much difference. I noticed that intake manifold pressure is too low at idle. It's only 12.9inHg at idle as you can see on the screen and 12inHg showing on gauge. Not sure how much it should under load when on plane but seems very low.
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    It's 2016 MPI engine. No distributor. Ignition coils controlled by PCM112 module
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    Hi everyone. I'm trying to figure out what's wrong with my engine. Noticed it won't rev above 4300 and fuel consumption is 30% higher than usual at 3000rpm and 50% at 4000rpm. It's 4.5l 250HP Mercruiser Bayliner VR5. Compression 180psi each cylinder, new TMAP and O2 sensors. See attached...
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