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  1. #1
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    2010 Optimax 150 misfire

    Hey all

    Have at least one misfiring cylinder in my 2010 Optimax 150 (edit: SN#1B787536). Have narrowed it down to cylinder(s) #5 (definite) and possibly also #3, both are on starboard side. Max RPM 4000 and rough idle. Noticed the problem at the lake, a few hours later in the day when running, it ran normally briefly before again losing power.

    Have swapped out coil, plug, and wire on #5 with #1 (which I know to be firing) with no change. Plug in #5 was wet and smelled like gasoline when pulled. #5 side injector had enough gasoline built up behind it to pop out the injector when I pulled the allen screws - I don't know if this is normal but it didn't happen when I pulled the injectors for #1 or #3. All three injectors tested on my (very cheap) meter at 2.1ohm.

    Where should I be looking next?
    Last edited by tr20josh; 01-03-2023 at 02:08 PM.

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    #2
    so your saying there is not sprk on #5 and possibly #3 , always relieve pressure on rails of both air and fuel before attempting any repairs , possible pcm failure
    .................................................. ...the scariest thing in life is the unknown ...................................

  3. Member
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    #3
    Quote Originally Posted by JOE54 View Post
    so your saying there is not sprk on #5 and possibly #3 , always relieve pressure on rails of both air and fuel before attempting any repairs , possible pcm failure
    Correct, no spark on #5. Engine bogs a bit when I disconnect #3 and revs somewhat when reconnected but does neither as strongly as #1 or #'s 2, 4, or 6. Point noted regarding relieving pressure on rails. Is there a way for me to test PCM?

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    #4
    test wiring harness if all found to be in spec pcm needs replaced
    .................................................. ...the scariest thing in life is the unknown ...................................

  5. Member
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    #5
    Does this engine have coil drivers? if so id be checking them .. i think on my 2004 #2 and #5 use the same driver
    2004 Stratos 285 Pro XL 150 Hp Optimax OT862351

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    #6
    thats why we need ser numbers
    .................................................. ...the scariest thing in life is the unknown ...................................

  7. Member
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    #7
    Quote Originally Posted by JOE54 View Post
    thats why we need ser numbers
    1B787536

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    #8
    150 optis 1b490866 and up has no drivers for coils
    .................................................. ...the scariest thing in life is the unknown ...................................

  9. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #9
    Please perform a SPARK TEST on the engine, with it running at idle. Use a timing light to clip onto each plug wire, one at a time while watching for flashing pattern.

    Thanks!


    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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    #10
    Quote Originally Posted by EuropeanAM View Post
    Please perform a SPARK TEST on the engine, with it running at idle. Use a timing light to clip onto each plug wire, one at a time while watching for flashing pattern.

    Thanks!
    Thanks Don, just ordered a timing light that will be delivered tonight and I'll perform this test tomorrow or this weekend.

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    #11
    Quote Originally Posted by EuropeanAM View Post
    Please perform a SPARK TEST on the engine, with it running at idle. Use a timing light to clip onto each plug wire, one at a time while watching for flashing pattern.

    Thanks!
    Please excuse my delay, school started and then had a death in the family so I haven't been able to get to this.

    I'm not experienced with a timing light but I connected an inductive timing light to each spark plug wire and observed flashing on all 6. I did not use it to check timing but just observed that the light flashed when connected to all wires, including the misfiring cylinder (#5). Is there anything more I'm looking for here?

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    #12
    Did all the sparks seem to spark a steady normal flash? Especially the bad cylinder?
    Mercury 2002 200hp Carbed Saltwater
    OT566776
    2002 Cape Horn 22' Bay

  13. Member
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    #13
    Quote Originally Posted by leonreno;[URL="tel:12872358"
    12872358[/URL]]Did all the sparks seem to spark a steady normal flash? Especially the bad cylinder?
    No observable differences between any of them. All seemed steady and at the same rate

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    #14
    Quote Originally Posted by tr20josh View Post
    Correct, no spark on #5.
    post #3 ////// you have checked compression on that cylinder havent you ???????? procede
    .................................................. ...the scariest thing in life is the unknown ...................................

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    #15
    Quote Originally Posted by JOE54 View Post
    post #3 ////// you have checked compression on that cylinder havent you ???????? procede
    I performed a compression test on all cylinders yesterday, all were within 10% of one another as expected.

    Also performed a spark test by holding the #5 plug against the block while a helper turned the key and observed spark from the plug. The plug was wet when I pulled it so it has gotten fuel during the limited periods (<10 minutes) it has been run in the driveway.

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    #16
    swap plug #5 to another cyl ,bad pulse pump diaphragm can foul #5 , broken reed valve possibility too
    .................................................. ...the scariest thing in life is the unknown ...................................

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    #17
    Just to eliminate the possibility, I would check the exhaust tuner hasn't fallen off, your motor has similar symptoms to what mine had. I chased ghosts for almost 12 months before I found the problem.

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    #18
    Quote Originally Posted by JOE54 View Post
    swap plug #5 to another cyl ,bad pulse pump diaphragm can foul #5 , broken reed valve possibility too
    I've swapped the plugs with #1 and since replaced the original plug from #5, both to no avail. Will attempt to inspect reed valves next.

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    #19
    Quote Originally Posted by JOE54 View Post
    swap plug #5 to another cyl ,bad pulse pump diaphragm can foul #5 , broken reed valve possibility too
    Broken reed valve looking like a possible culprit. Checked inside air plenum with a curved mirror and was able to clearly see two reed blocks. One had four as normal; the other only had 3, and where the fourth one should have been, I could see two bronze/gold circles, I assume something that's normally underneath a reed?

    Have any tips/a guide on removing the plenum so I can access the reeds?
    Last edited by tr20josh; 02-12-2023 at 05:48 PM.

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    #20
    Factory service manual will cover everything and you will need an in lb torque wrench. You should replace the plenum gasket when you do this, and if you pull the reed plate, the gasket behind it as well. If your reeds are still steel, replace with TDR.

    Can see the process here, although it covers fuel rails and DIs, I also replaced reeds - Fuel Rail and Direct Injector Removal
    _______

    Phil
    '09 Hewescraft ProV
    '09 150 Optimax


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