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  1. M

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

    This engine never really gets stabilized enough to look in depth. The fuel and ignition tables are changing to often for me.
  2. M

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

    Yes I looked at the chart --- it's the same chart that's in all the manuals since the beginning of time. I noted that it starts with "most engines" seeing as that chart has been around since points and carbs, I would say you don't fall under that category. I also noted that under low vacuum...
  3. M

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

    I haven't had much time today to spend on this, but I did want to cover the most important part ---- electrical system. There are a lot of checks, calculations and choosing of all the tables that happen during starting, so correct power is critical. This is why I recommend that during starting...
  4. M

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

    They didn’t mention any problems with the keyed ones in school, good to know. I’m guessing that at least you could poke something through the CPS hole and get it to wiggle.
  5. M

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

    The other side of that coin. These newer engines will alert you before they ever get that carboned up, so it will never happen. Sold a new EFI 10 hp last month, we wouldn’t take his 1994 10hp on trade because it was too old Even though “it runs really good”. He called two weeks later and was...
  6. M

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

    Funny thing—- maybe because I understand the new systems, I find them easier to diagnose. Especially if it has cats. Another funny thing—- even though I work in an industry that turns fossil fuel into CO. I still have some pretty strong opinions about pollution and what it’s doing to the...
  7. M

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

    If it walked out of position, yes. If it spun a little bit, that got rather involved. But I’ve never had to do it, so not 100% sure.
  8. M

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

    Yes but still helping on the MerCruiser front. i looked up one of your Diacom files to see your MAP readings.👍🏻
  9. M

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

    What do you see wrong with fuel consumption? It's tracking with MAP, Demand and RPMs O.P. has never stayed stable on the throttle long enough to get into ARO (advanced range optimization) where they will get best fuel burn. This is one off the things Diacom doesn't display like G3 does.
  10. M

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

    Nope, not needed with this system, just like no knock sensors. Only used on the new stuff that has VVT - variable valve timing.
  11. M

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

    This engine adjusts timing for each cylinder separately. And like I said #s look normal. You wouldn't check timing with a timing light. You use a dial indicator and it's a really big pain in the azz. It's not ajustable.
  12. M

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

    Spark advance looks pretty good to me. But once again --- low cranking volts could affect this. Did you mean ° degrees or % percent? What sensor are you thinking of? But that does bring up a somewhat exotic possibility. I've never seen it, but in class the instructor does bring up the...
  13. M

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

    I really don't think you have a problem with lifters or cam timing. Your fuel trims look too good. But if I had some good O2 numbers I could be more sure. Also with the electrical problem you have, all bets are off on these numbers. The PCM Diagnostic manual gives a little info on how all this...
  14. M

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

    Didn't know you were on the other side of the pond! I have NO idea how this might affect anything. The only thing I know about prepping a boat for Europe is from many years ago having to install a special transformer for shore power on a boat heading there. That was back in the Days of MEFI so...
  15. M

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

    What should be 5-15%?
  16. M

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

    NO. I keep saying these MAP readings are normal. While I don't have any other 4.5 Diacom REC files to compare (I have always used Mercs G3 on these engines because I'm at a dealer and I now work the parts counter and no longer have access to G3) but, I do have a bunch of Diacom REC files for...
  17. M

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

    What was the alarm?
  18. M

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

    My bad! I missed that this ISN'T a cat engine. Please disregard everything I said about PID, O2 and Misfires.
  19. M

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

    After 40 years of working on boats I don't trust those charts. No mention of elevation. No mention of ambient temperature No mention of amount of weight in boat. No mention of water/wave conditions. All four of these variables can have a big impact. You posted earlier that you're thinking...
  20. M

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

    That chart is at idle. But you posted. "Fuel pressure steady at 45psi - checked under load while on plane." Under load should be about 5 psi higher. If you look about 30 pages deeper into the manual, you will find 50-54 psi with reference line removed. Removing the reference line will bring...
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