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  1. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #21
    I would suggest utilizing your DDT to perform a Cylinder Misfire Test at WOT.

    Record the RPM drop for each individual cylinder- let's see if any one cylinder is significantly lower than the others


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
    Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
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    #22
    Don, I already did that and it only dropped about 100 rpm on each cylinder. I may have found an issue since the
    return fuel enters against the boost pump pressure. I can't find anywhere what the boost pump pressure is supposed to be
    but mine is 36lbs which might be too high? I had just got this boat and the previous owner has had the fuel rails rebuilt and I have the flow
    sheet on all the injectors before and after.
    Last edited by topwater1956; 11-25-2018 at 05:53 PM.
    Terry Tanner

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    #23
    You only lost 100 rpm per dropped cylinder at wide open throttle? Something isn’t right here...
    David Patten
    Automotive and marine technician.

  4. Member lpugh's Avatar
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    #24
    Terry have you addressed the pressure readings in your first post? I do not know the exact specs but I think this motor requires a 15 psi difference between fuel and air pressure, your readings indicate 10. If I am correct your reading would indicate to me a you have a serious low volume problem. Differential pressure must be exact for injectors to flow the proper amount of fuel and the correct pressure
    Thank You Leon Pugh

  5. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #25
    Quote Originally Posted by lpugh View Post
    Terry have you addressed the pressure readings in your first post? I do not know the exact specs but I think this motor requires a 15 psi difference between fuel and air pressure, your readings indicate 10. If I am correct your reading would indicate to me a you have a serious low volume problem. Differential pressure must be exact for injectors to flow the proper amount of fuel and the correct pressure
    +1... Believe they were actually showing a 20# differential.

    See Post# 8 where this is mentioned.


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
    Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
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  6. Member lpugh's Avatar
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    #26
    Terry and Don, I was thinking about this post and how the automotive field calculates fuel mileage and thinking we have very useful diagnostic tool with the smart craft. I am sure it works in the same way as automotive soft ware does. It calculates fuel used by the total injector open time and by assuming the fuel pressure is exactly as designed it can be very precise on fuel used. My point being if the smartcraft says you used 20 gallons today, you should have used twenty gallon from the tank. If only 18 gallon were actually consumed you need to find out why the system only flowed 18 gallons. Which brings me back to pressure differential. Fuel pressure could be correct but if air pressure is high differential would be low resulting in lower flow. Of course other things could cause the low flow but I do believe the fuel used could a useful tool to help verify a degrading fuel issue that at time may be difficult to actually pin down. If consistently using less than the smartcraft indicates I would bet there is a problem with pressures, restricted injectors or aerated fuel

    What do you think Don
    Last edited by lpugh; 11-27-2018 at 09:42 PM.
    Thank You Leon Pugh

  7. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #27
    Theoretically that's correct, Leon. The catch is that the boat will almost never sit at EXACTLY the same attitude every time it's filled, which can alter the exact amount you "can" add to the tank. There's probably higher odds of an error here than in the PCM Map Tables.

    That being said- if the fuel pressure is really at 115 psi, that's going to result in considerably more fuel being delivered than is intended.


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
    Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
    Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor

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    #28
    I forgot to mention in my first post that I threw away those old gauges and bought some liquid filled, popped the plugs
    out of the air and fuel regulators and adjusted the air @ 90 and the Fuel @ 110 with no change. This motor requires 15lbs difference and just out of
    curiosity I adjust to 10lbs difference, ran the same. I ran the fuel pressure down to 105 and the air to 90, no change. No matter what I done
    with fuel and air pressures it ran the same. I figured then that it had to be a sleeve had turned. Pull the heads and cylinders 1 and 2 were both turned quiet a bit.
    Terry Tanner

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    #29
    I forgot to mention in my first post that I threw away those old gauges and bought some liquid filled, popped the plugs
    out of the air and fuel regulators and adjusted the air @ 90 and the Fuel @ 110 with the motor running @ 1000 rpm like its supposed to be, no change.
    This motor requires 15lbs difference and just out of curiosity I adjust to 10lbs difference, ran the same. I ran the fuel pressure down to 105 and the air to 90,
    no change. No matter what I done with fuel and air pressures it ran the same. I figured then that it had to be a sleeve had turned. Pull the heads and
    cylinders 1 and 2 were both turned quiet a bit. After close inspection they didn't turn they were installed like this because you can see that they used a flex
    hone and hone marks are on the part of the block that the sleeve would normally cover up. To top it off they used a dirty hone and cut deep grooves
    in the cylinder walls instead of hatch marks. This is by far the worst hone job I have ever seen. This is a Mercury factory rebuilt motor 2 years ago with only 69hrs
    The PCM history showed the motor has never been over 5000 rpm since new. I see why.



    Last edited by topwater1956; 11-30-2018 at 09:30 PM.
    Terry Tanner

  10. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #30
    I don't think they were installed that way- the marks you see in the window of the sleeve are not from the honing process.

    Good catch- that would account for the problems you are having, for sure!


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
    Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
    Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor

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    #31
    Probably overheated.



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    #32
    Quote Originally Posted by EuropeanAM View Post
    I don't think they were installed that way- the marks you see in the window of the sleeve are not from the honing process.

    Good catch- that would account for the problems you are having, for sure!
    The camera doesn't show it very well but it looks like they used a ball flex hone and there are hone marks on the block in the sleeve window. It was definitely honed with the sleeve turned. I believe
    it was done like that from day one, because the DDT on the history showed 4500-4999 rpm 2.7 hrs----5000-5699 rpm 0 with a total of 571 hrs.
    Terry Tanner

  13. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #33
    Interesting- most turn or twist at low hours if they are going to (never seen one assembled that way).


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
    Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
    Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor

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    #34
    Quote Originally Posted by EuropeanAM View Post
    Interesting- most turn or twist at low hours if they are going to (never seen one assembled that way).
    2 months ago there was a guy across town from me that repowered his boat with a 250proxs and it wouldn't take off right or run very well. He took it back
    and they worked on for 2 days, finally pulled the heads and it had a sleeve in it like that. Mercury sent a new power head and it runs great now.
    Terry Tanner

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