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  1. #1
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    Optimax startup flare idle fluctuation

    2007 Mercury Optimax Pro XS 250 Serial #: 1B492182

    Ok I have another issue as follows:

    On first start of day the engine has a start up flare to 1600 rpm (neutral overspeed) and idle fluctuates for 30 seconds until warm. I check fuel air pressures and they are as follows:

    running:
    fuel: 105 / air 95

    shut down:
    drops to: fuel 95 / air 85

    5 seconds: fuel 90 / air 80
    10 seconds: fuel 85/ air 75
    15 second: fuel 80 / air 70

    Cycle key with no air pressure and fuel pressure quickly jumps to 35 psi and drops down to 15 psi. Holds at 15 psi.


    Seems like air pressure doesn’t hold tightly when I put shop air to it 80 psi and it drop 15 pounds in 15 seconds. Not sure if this is a normal rate.

    pinched return line of air regulator and checked for external leaks. No change. Removed and inspected tracker valve closely under 10 x magnifying glass and bright light no damage.

    fuel rails new injectors cleaned and air injectors new. Fuel system new ( all three pumps new. New lines and merc primer bulb)...

    Engine runs great just flare and idle fluctuate on cold start...

    After it warms it runs great the rest of the day.

    any ideas???

  2. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #2
    Don't expect your problem is in the rails/injectors, though the Pressure Differential is indicating the WRONG RAILS (where did they come from, and what PART NUMBER?)

    Pulse Fuel Pump been rebuilt?

    Checked for any other fuel leaks?

    Remote Oil tank level between 30% and 80% (NOT OVERFULL)?

    Spark plugs last replaced when?

    Thermostats been inspected and tested?


    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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    #3
    Quote Originally Posted by EuropeanAM View Post
    Don't expect your problem is in the rails/injectors, though the Pressure Differential is indicating the WRONG RAILS (where did they come from, and what PART NUMBER?)

    Pulse Fuel Pump been rebuilt?

    Checked for any other fuel leaks?

    Remote Oil tank level between 30% and 80% (NOT OVERFULL)?

    Spark plugs last replaced when?

    Thermostats been inspected and tested?

    My pressure gauge may be off. I have glycerine filled gauges on the way and will recheck.

    The part number for the rails: 8M6001787

    rails recently replaced under warranty. Originally bought new rails and air injectors and you cleaned the fuel injectors... there was an issue with the crossover air hose and the entire rail was replaced under warranty claim.

    pulse pump new last year.

    No other leaks.

    Remote oil tank is over 80% but I believe this has been doing this with less than 80% in oil tank...


    Time for new plugs... they are a year old and have 200 hrs on them

    Thermostats new... ( not sure if this will cause an idle flare with fluctuating idle on cold start?)

    Run Dons cocktail and DFI OIL every tank...

  4. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #4
    Looks like 8M0134248 is the actual Part Number (can't use numbers printed on Parts). Confirmed that in the engine History from this year.

    Plugs- definitely do them (I would not stretch beyond 1 year or 100 hours at the max). Seen too many plug failures with nasty results.

    Oil level too full in remote tank will cause oil to be dumped into the engine after shutdown (potentially).

    After you get the right type of gauges, recheck readings (and swap connections to make sure the results match with either gauge on the air side).


    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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    #5
    Quote Originally Posted by EuropeanAM View Post
    Looks like 8M0134248 is the actual Part Number (can't use numbers printed on Parts). Confirmed that in the engine History from this year.

    Plugs- definitely do them (I would not stretch beyond 1 year or 100 hours at the max). Seen too many plug failures with nasty results.

    Oil level too full in remote tank will cause oil to be dumped into the engine after shutdown (potentially).

    After you get the right type of gauges, recheck readings (and swap connections to make sure the results match with either gauge on the air side).

    Update:

    I received the glycerin filled gages and my numbers are as follows:

    running:
    air 90 psi / fuel 105 psi

    shutdown:
    5 seconds air 84 / fuel 94
    10 seconds air 78 / fuel 88
    15 seconds air 72 / fuel 82

    i checked and my oil is like 95 percent.
    I will remove some and replace plugs and go from there...

  6. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #6
    Report back after you've run it a couple times... you may be right on the oil level.


    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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  7. Member
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    #7

    Update

    Quote Originally Posted by EuropeanAM View Post
    Report back after you've run it a couple times... you may be right on the oil level.
    Ok, fished a tournament last Saturday and the engine did not flare. I replaced the plugs with NGK-IZFR6J properly gapped and torqued. Engine ran great all day except one last issue...

    When I shut down after a long idle or under certain conditions the heat soak temp rises pretty high. I saw 168 at one point during a restart shortly (within a few minutes) after a shutdown.


    Im not sure what is causing this or if this is something to be concerned about. I had a cracked crank case half cover and do not want that to happen again. Not sure if this is the cause and is subliminal issue because when I shut down I don’t know how high it rises each time because the key is off when I fish. If I restart shortly after shutdown I notice it rises high. I did not get an over temp alarm so not sure if I should be concerned...



  8. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #8
    Are you turning the key on (engine off) to read that 168 degrees?

    Normally you should start the engine within 5 seconds of turning the key "on", as there is programmed logic to ignore temps within "normal" heat-soak ranges for a short period of time.

    If the engine was tilted up and shut down, it's not at all uncommon for it to heat-soak into the 160's


    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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    #9
    Quote Originally Posted by EuropeanAM View Post
    Are you turning the key on (engine off) to read that 168 degrees?

    Normally you should start the engine within 5 seconds of turning the key "on", as there is programmed logic to ignore temps within "normal" heat-soak ranges for a short period of time.

    If the engine was tilted up and shut down, it's not at all uncommon for it to heat-soak into the 160's

    I had an issue with raising my engine jackplate and when I raise the jackplate above 2” below pad I’d get an overtemp on start up in the past.

    Overtemp normally happened after a long idle (no wake zone) and shut down and would heat soak and when I crank within five seconds (engine always down) it would set an over heat alarm.

    I installed the water intake plugs in the lower unit 3 total each side, although I don’t believe my pickup holes in the lower unit were ever out of the water when it happened. I lowered the engine to 2.5-3” below pad and I do not get the over temp after startup (just rises to 168). I just check it and see that it rises to 168 under certain conditions.


    I am aware of what you pointed out and the motor is all the way down and there are times when I crank it within five seconds and it ignores the temp and it drops to normal. Other times it would set an over heat alarm with engine down and crank within five seconds. The concern is the over temp when I restart with the Jackplate above 2” below pad. I have the plugs 3 total on each side in the pickup with a low water pickup in the lower unit.

    Does the computer monitor time or does it monitor the pressure sensor?? is it possible the pressure doesn’t rise when the computer looks for it??

    With the jack plate raised above 2” there are times when I get an over heat alarm with the engine down and crank within five seconds.

    some times it ignores it and other times it doesn’t I believe if there is a rise in temp after start it sets the alarm. If it sees it start to drop it ignores it...

    all cooling system components are new.


    not try to be too confusing...
    Last edited by Basshead35; 12-17-2019 at 02:06 PM.

  10. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #10
    PCM is monitoring temp and pressure- the "time" ignored applies only where the PCM perceives it may be a simple "curable heat soak". For a hypothetical example:

    One warm start is at 168 degrees... engine starts, PCM sees temp begin to decrease within 10 seconds. At 15 seconds, water pressure begins to climb. PCM logic ignores and does not log any sort of overheat.

    Another warm start is at 174 degrees... engine starts, PCM sees temp rise to 176 within 10 seconds and logs an overheat fault. 15 seconds later, water pressure begins to climb and temp begins falling. PCM sets the status of the fault as "inactive" (no longer occurring).

    I believe you will find that the situation is more related to how high you have the engine, rather than how many holes you are plugging in the gearcase. As the engine sits higher, the pressure against the water inlets becomes lower (allowing the weight of the water in the engine block to cause a higher "head" pressure in the water supply tube and exhaust, which results in all or most of the water that might normally remain in the block being drained back into the lake, and leaving very little (if any) water in the block to help absorb the heat that is radiating from the block castings).

    You can probably prove this yourself by observing the difference that 2" lower height will cause.

    On a side note- and NOT saying this is the case, gasket leaks at locations such as the adapter plate or powerhead gaskets will exasperate this scenario significantly.


    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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    #11
    Quote Originally Posted by EuropeanAM View Post
    PCM is monitoring temp and pressure- the "time" ignored applies only where the PCM perceives it may be a simple "curable heat soak". For a hypothetical example:

    One warm start is at 168 degrees... engine starts, PCM sees temp begin to decrease within 10 seconds. At 15 seconds, water pressure begins to climb. PCM logic ignores and does not log any sort of overheat.

    Another warm start is at 174 degrees... engine starts, PCM sees temp rise to 176 within 10 seconds and logs an overheat fault. 15 seconds later, water pressure begins to climb and temp begins falling. PCM sets the status of the fault as "inactive" (no longer occurring).

    I believe you will find that the situation is more related to how high you have the engine, rather than how many holes you are plugging in the gearcase. As the engine sits higher, the pressure against the water inlets becomes lower (allowing the weight of the water in the engine block to cause a higher "head" pressure in the water supply tube and exhaust, which results in all or most of the water that might normally remain in the block being drained back into the lake, and leaving very little (if any) water in the block to help absorb the heat that is radiating from the block castings).

    You can probably prove this yourself by observing the difference that 2" lower height will cause.

    On a side note- and NOT saying this is the case, gasket leaks at locations such as the adapter plate or powerhead gaskets will exasperate this scenario significantly.


    Ok, I do know that other people run optimax engines on the same boat (07 Blazer 202 Pro V bass boat) at higher jackplate settings. I will just have to keep an eye on it...


    The power head gasket is new, but the adapter plate gasket hasn’t been changed since I’ve had the boat. The power head gasket did have a sheet that shows a special torque sequence that I followed. It came with the power head gasket set I bought during the rebuild. I followed the torque sequence. I don’t know of any way to tell if either of these two could be causing this problem if at all.

    I will keep an eye on it..