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

    It doesn't? See attached screen at 2857rpm. Steady spark advance injectors for as long as rpm stays the same. Do you expect see anything more if its 2min or 5min?
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    Vacuum chart is in the manual and it's copy and paste since the beginning of the time just because its simple engine with OHV. That's what I think. It ain't diesel or any modern engine. Guess its there because is applicable. Fuel rail pressure also proves that its not in the range. And yes I...
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    Once agian thanks for your time and effort- much appreciated. Battery probably needs replacing but 10-10,5V voltage drop during cranking is acceptable relaying on many internet sources. You mention drop above 0.5V is bad. I will test battery anyway and if its OK then check electrical system...
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    Attached file with two latest recordings. Please feel free to comment if you notice something unusual
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    Diacom data for 4.5l 250HP Mercruiser

    Hi everyone. Is someone here who has or can get Diacom recording for 4.5l 250HP Mercruiser? I would like to get them to compare with my engine. It's PCM112 ecu version
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    If you want you can install Diacom and check files. If free and it will work. I will appreciate another point of view.
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    I checked in service manual its a keyway.
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    I will do and hope will find it with your help guys
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    Took that sensor out earlier to check for potential dirt - I guess its magnetic. I will try with screw driver but will I see any movement if it slipped? Worth to try anyway
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    Unless you have the specs your ''ball park'' is guessing as well ;)
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    Can you tell from drawing below. I can't see key there. https://www.mercruiserparts.com/bam/subassemblydetail/51242484/28214545
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    I know fuel trims and, o2 target and o2 sensor response looks perfect. But what in the situation that the timing is wrong. What if fuel burns too late when piston already moves down and some of combustion goes out through exhaust valve opening to early. Will o2 sensor notice any difference? It...
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    Thought you noticed that I don't write like native. The only time theboat is connected to power here is to charge battery and regardless if its US or Europe it will always get proper DC supply from battery charger.
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    17-21"Hg probably some general info found online - sorry my bad. But there is page in service manual for this engine that specifies that. See attached. Only difference that it states normal as 15-21Hg. Did you see my fuel supply module checks? Fuel pressure is not in the proper range either not...
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    I'm not sure what timing should be as well as other things that's why started this post and asked for help with checking Diacom data. TMAP was verified - diacom readings vs physical gauge. Both show the same. Not sure why sea water temp is always 32F. This engine its Mercruiser own design and...
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    Thats correct. Not sure what's the logic of this PCM. Speed and density controlled. There is no IAC just throttle drive by wire. Guessing that PCM calculates air density from vacuum and temperature (TMAP sensor) and adjusts injector pulses to keep stichometrtic ratio. How does the RPM stay...
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    Yes I did remove oil cap - no smoke there. Did not check timing old fashion but will it work if PCM controls timing and shows already -3 deg at idle? Broken valve spring - don't think so compression 180psi each cylinder. I will definitely remove intake and check valve springs and clean...
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    Tried that while ago no leaks. Sprayed everywhere around intake and injectors. And this PCM wont change rpm even if sprayed engine starter into throttle body - tested to see reaction. Noticed only fuel consumption going gown immediately on vessel view. Checked also with smoke generator no leaks.
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    There's only the potmeter on shift plate and it sends signal to PCM and PCM controls the throttle body (drive by wire). Is that what you asked for ?
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    @muc what do you think of oil pressure? Only min oil pressure is specified in service manual 41kPa, mine is 280 at idle and 330 at 3000rpm. I'm just wondering if excessive oil pressure could be causing hydraulic lifter pump-up which in turn keeps the valves slightly open preventing the engine...
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