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  1. #1
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    200 opti idle and low rpm surging

    2001 Optimax 200, manufactured in 2000 (OT273874). Motor has approximately 140 hours. The last two times out the motor has displayed a surge at idle and low rpms. In forward gear, the surge is very rhythmic between approximately 700 and 1,000 rpm. The rpms surge up and down +/- 100 in a rhythmic fashion and is most distinct at the lower end the spectrum. While idling the surging is a bit more sporadic and could be described as miss. Occasionally sounding as if I would stall, but never does.

    Previously in the season, I had an issue with stalling while idling or during low rpm scenarios. Eventually, the motor threw a beep/fault. It was an open injector fault on #6 direct injector. Took it to my service tech and they reported the harness/clip to the #6 direct injector was still clipped in place, but visible separate. This caused the remaining cylinders to flood and unable to start. After the harness was checked and reconnected, the motor was flawless for over a month and approximately 6-8 trips.

    Early this spring, and prior to any issues, I completed the fuel line, bulb, etc. upgrades as stated in the sticky. Was certainly needed as I was running on the original components and they were about disintegrated internally.

    Once past approximately 1,000-1,200 rpms, motor has strong and consistent hole shot with good top end. I do need a different prop though as I know I am overpitched and about 500-600 below where I should be.

    Just looking for opinions on thing to look for or ask about when I take it in for winterizing (live in Wisconsin, so 'winter' is never too far away!)

    Thanks in advance!

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    #2
    Set the prop pitch on the motor properly FIRST before digging deeper.



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    #3
    Up to date on other maintenance, plugs, fuel filter, etc? As for winterizing print this and share with your tech - Recommended Annual Maintenance or Winterization for Optimax Engines
    _______

    Phil
    '09 Hewescraft ProV
    '09 150 Optimax


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    #4
    I should have confirmed in my initial post. However, the spark plugs, fuel filter, etc have been changed annually (changed May of this year). I also had thermostats checked and replaced a warped gasket. Fuel pressures were also verified/confirmed at this time, but this was obviously before I experienced the issues I described.

  5. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #5
    See posts 2-3 for good advice on where to start.

    Check those air/fuel pressures at idle, under acceleration, and 5/10/15 seconds after shutdown.

    Also verify PULSE FUEL PUMP is properly assembled. Triple check if necessary.


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
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    #6
    I thought I would reply to close the loop on my previous issue. I took my boat in for annual service this spring to my usual Mercury Certified Technician. Among the annual maintenance, I explained the surging I had at low rpms and idle. I also scheduled a time to test out a new prop. Air/fuel pressures came back high, as well as a high MAP sensor output. Sensor readings were not enough to cause any faults but were noted when check with pressure gauges and/or reviewed on DDT. I reminded them of my previous issues with an occasionally open fault on #6 DI. They found this very interesting. After digging into it further, they found a few reeds were not closing fully due to some rough spots on the cages. They also flow tested and resistance tested all DI. Sure enough, #6 DI did not pass the resistance test (came back at like 2.4 ohms) and would frequently stick wide open.

    They repaired reed cage and also replaced ALL 6 DI's with used/flow tested Blue DI's. I also purchased a prop, allowing me to just touch 5,750 when lightly loaded Needless to say idle, hole shot, and throttle response are much improved.

    Since then however, I have developed a slightly rough idle. This only occurs on the first cold start up of the day (and yes I do pump bulb firm at every start). It almost can be described as a occasionally miss. It did stall on me once. As soon as I apply throttle to back away from dock, it smooths out. By the time I get away from the dock and through the no wake (~3-5 minutes), I can drop back to idle and I purrs as smooth as the rest of the day.

    Any thoughts? Fuel line and bulb are 1 year old and hold firm. I'm thinking thermostats but do no have smartcraft to verify. I just learned my engine vintage would qualify for the SC1000 system. So that will likely be the next item on my list.

    Thank in advance.

  7. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #7
    Check thermostats, plugs and plug wires before looking too "deep" on this.


    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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  8. Member lpugh's Avatar
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    #8
    I did not see any mention of fuel injector flow testing or service, as well as what was mentioned above might be a good idea to read this information http://www.bbcboards.net/showthread.php?t=20401
    I have seen a lot of minor problems resolved by following this. That is a lot years of service for injectors to be trouble free, though following those recommendations it is very possible to never have injectors issues other than occasional electrical problems with one
    My last optimax I had a similar idle problem as you described and started adding the premium plus to the fuel and after about 2 tanks of fuel the idle returned to perfect. I was already using top quality fuel and Quicklean. I was pleasantly surprised by how improved cold idle was
    Thank You Leon Pugh

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    #9
    Fuel injectors were not flow tested. Only the used DI's. I run the cocktail and treat all my fuel. I recently switched to 91 octane to see if that would help. Coincidentally or not, the idle issues disappeared for the next 4-5 outings. I was convinced going to a slightly higher octane with no ethanol had been the solution.

    Well, I went out this morning and experienced similar rough idle conditions. It misses as if it almost stalls and then catches itself. Applying additional throttle to ~800 rpms typically smooths it out. I did notice a small puff smoke upon initial start up this morning. I'm not sure if that is unusual or if humidity/dew point happened to be just so. Also, if I went on an extended run, set back down, and dropped to idle, the idle would be absolutely smooth. All plug wires and connections are good. All DI & FI connections are good. Also pulled covers off thermostats and did not see any debris causing them to hang open.

    Upon further inspection this afternoon, I noticed my shift position switch had a generous layer of grease/lubrication on it. I cleaned the area, but have not tested the engine since. I also have not pulled any plugs but that may be next.
    Last edited by BBallFisherman; 08-17-2019 at 05:02 PM.

  10. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #10
    Check those plugs... and really need to drop back to the correct fuel (87 octane, or if you really feel there is an idle improvement, no higher than 89).


    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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    #11
    To clarify. I had a little over half a tank of 10% ethanol 89 octane (probably 2 months old), and filled with non-ethanol 91. So it wasn't a full tank of then 91.

    Update.....pulled plugs and they looked outstanding. No visible hairline cracks or evidence of fouling. All were very clean and looked almost identical to each other. Amazing, what the appropriate prop and clean DI's can do. For fun, I checked the throttle plate gap with a 5/64 drill bit. Depending on the angle, I would say it was more than a snug fit. My opinion would be that it was something less than 5/64. While I was at it, I advanced the throttle (key off obviously) and had a look at the reeds via 21st century mirror (cell phone camera). I couldn't see them all, but I did not see any obvious signs of cracks or chips. I know this isn't the best, or correct, way to inspect the reeds but I was just looking for any glaring observations.

    The part that has me stumped is why it only demonstrates the miss/stumble on a start-up? Why is the idle so much smoother after a short run?

  12. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #12
    PCM has programming that delivers significantly more fuel when the engine is cold. Once the engine reaches approximately 112-120 degrees, the fuel mapping jumps from a "multiplier" table to the standard table (under which the warm engine will run much smoother).

    Much like a choke on an older engine. Engine should ALWAYS be run to operating temperature before accelerating (120+ Degrees F).


    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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    #13
    Don, thanks for the insight. Is there anything else I can check into or do to potentially remedy the situation? I suspect next would be fuel/air pressures at idle and 5/10/15 seconds after shutdown. Otherwise, I'll just keep running her and make the switch back to 87 or 89 fuel with the usual cocktail. Thanks for everyone's help!

  14. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #14
    Address the simple thing first (the fuel)- and see how it does before going to a lot of effort or expense. And of course make sure it's coming up to temp on BOTH banks of cylinders.


    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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    #15
    So I had some time this morning before hitting the lake and thought I would quickly physically test my thermostats, confirming they woudl come to temp, since I do not have smartcraft (yet) and it only takes a few minutes. I've only had to pull the thermostats twice before, but I don't know how I never noticed this.......Upon inspection, I see each thermostat is stamped (120 degrees) and part 850279-2. Covers are 858856C & 858857C. I suspect these are the incorrect stats and covers.

    I'm a bit irritated because when I stopped by the service shop/dealer of the original owner when purchasing the boat a few years ago, I was with the understanding these were changed out with a service bulletin in 2001 (someone on here could probably confirm that with my engine serial number above). It appears that is not the case.

    I don't suspect this is attributing to my recent idle situation, but likely something that should be resolved nonetheless. If someone could please confirm, I'll likely be contacting Don/Rhonda for appropriate parts.

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    #16
    Another update. Ran the boat on Sunday. On the first cold start, within 5-10 seconds, the idle was rough and eventually stalled. Checked primer bulb and it was firm. Turned over again, and was smooth as silk. Parked the truck and came back. Motor was still running and idle was still smooth. Ran around for a while and put the boat on the trailer. Went back home to get the wife and kids an headed out to another lake. Dropped the boat in the water, pumped bulb, turned key, fired up with no misses or indications of rough idle. This would have been about 1.5-2 hours after shutting down and putting the boat on the trailer at the first stop. Hmmmm??? Puzzled. Still running on same gas, so have not filled up recently.

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    #17
    Did you pump up the primer bulb BEFORE the first start?



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    #18
    Yes sir. I always pump the bulb firm before EVERY start.

  19. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #19
    History does show the thermostats were updated in 9/01. However... that doesn't mean something else didn't occur outside of warranty (such as powerhead replaced with another that did NOT have the updated thermostats/covers).

    Definitely plan to get those updated. Outside of that... going to be hard to fix it until it at least "acts" like it's broken.


    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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