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

    Fuel quality causing low intake vacuum? Its 95 octane exactly name E10. Spark plugs are correct.
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    Not sure because nothing showed up on Diacom. Guessing low water pressure
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    Can we now all agree that low vacuum is what I should be sorting out first? Today checked intake manifold with smoke generator. No leaks Any other ideas what to check?
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    @muc I also checked fuel supply module and it works nearly as it sholud. 1st video - ignition on the pressure goes up to 51psi. Then at idle stays steady 46psi. According to manual it should be 40-45. Its 1psi above acceptable range because its regulated by vacuum pressure and if this is too low...
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    @muc please see the attached Diacom recordings. The engine stopped due to an alarm, so the log is split into two files. Hope this is sufficient.
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    No way I thought its gonna be easier than that. Is it any other way to verify timing chain? IDK maybe measurement of valves and piston movement? I will run Diacom tests today. Vacuum stays at 12.5"Hg reading on gauge with engine warm up that's I'm sure and I think I should focus on sorting...
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    @muc Checked manual and 45psi is correct fuel pressure for that engine.
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    Props - turning point 14.25x21 and I thought that boat was sluggish because of that and replaced with SS 14.5x19. As long i won't see correct vacuum pressure I will be barking under that tree 😉
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    @muc when it comes to drive im pretty sure with correct ratio. I checked online Bayliner VR5 performance done by boating magazines and at 3000rpm and 4000rpm a get exactly the same speed as they did during boat test. If prop or gear ratio was different than what they had in test boat speed won't...
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    I will take engine photo tomorrow. It's version with only one O2 sensor per exhaust. I was getting confused with that mercruiser site with parts too. Its not very clear there with serial numbers etc. That sticker tells you all about catalyst - not for sale in California.
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    I know what diacom shows in regards to MAP explained it to someone just like you did few days ago under post #18. During Diacom test vacuum gauge was connected to manifold and never showed more than 12.5" on idle. BTW see attached. It's below 13"
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    It's alpha one gen 2. 1.62 ratio if I rememeber right
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    Found screen shot from month ago and water pressure was much higher. It all changed that one day. Engine keeps right temperature maybe just pressure sensor is restricted. I would expect overheating if watter pressure is 1/5 of what it was few weeks ago.
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    I will do it again tomorrow then and get some decent data. When I did the recording you just reviewed noticed that engine was warmed up, got on plane waited for O2 status to change to closed loop and I was sure that it was the whole PID ongoing. What else to look for to be sure that its in...
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    @muc please see attached the recording of my previous checks. Idle, then steady plane at 3000, 4000 and WOT
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    Do you know what was wrong with it back then? Was it repaired before auction or sold as it was?
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    BTW where did you get that information about warranty return? Can I see the source please
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    What I've got is the recording of more or less what you pointed here, but i posted only snapshots. Will do another test anyways.
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    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    I've been on it for weeks. Checked props, outdrive ratio, replaced gimbal bearing before summer, tried 2 props, even weighted boat to see if there is no extra load. Only what found is vacuum pressure its 12in at idle and 0.5 at WOT. At 3000 7in and at 4000 3in. Correct at idle is 17-21. All...
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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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