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  1. #1
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    Question 115 Mercury Optimax 2004

    Hi,

    I'm working on diagnosing what caused cylinder 1 to lose all compression on a Mercury Optimax 115. Serial #: 0T920655. 2004 115ELPTO

    The outboard starts great, idles fine and can even get the boat up on a plane. It cannot reach full throttle (climb to higher RPM is very slow). At full throttle position, after reaching a higher RPM (boat planed out), the engine dies.

    I bought this boat and outboard with full disclosure that the outboard was 'not good'. I went on one test run on a nearby lake. Before my test run cold compression numbers (I didn't want to do more damage than I had to, I get it, these numbers are not good for much) 1: 30psi, 2: 90psi, 3: 90psi. After the test run #1 (engine still warm) had dropped to 0psi. By #1 I mean the top cylinder as described in the service manual.

    I have the Mercury service manual and I'm reading through it, "hatching my plan". I also bought the Diacomm cable.

    Here are a couple photos I took with a borescope through the sparkplug holes. The first two are of #1, I couldn't see any cross hatching, where the last two images of 2 and 3 have quite a bit of crosshatching still visible. There's also more carbon that looks more wet in 2 and 3. Seems #1 was hot.
    https://postimg.cc/gallery/2y0p2fhca/

    I'm hoping to find root cause before I tear everything apart, gauge the bores, order parts, and start rebuilding. Current theories involve running lean with a bad or dirty fuel injector or leaking direct injector. And/or low flow from the oil pump, bad oil check valve, plugged hose, etc. I did verify with the diacomm cable that all the injectors fire (sound/vibration from each) but have not removed anything to verify actual performance.

    Any theories, ideas, tips, or tricks?

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    #2
    check fuel system very close send inj and rails to be cleaned and verified, you have to pull crank and pistons first before gaging bores they come out from front, no cyl head on that one
    .................................................. ...the scariest thing in life is the unknown ...................................

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    #3
    Quote Originally Posted by JOE54 View Post
    check fuel system very close send inj and rails to be cleaned and verified, you have to pull crank and pistons first before gaging bores they come out from front, no cyl head on that one
    So you're thinking more running lean and hot than an oil problem? Anything to do before tearing it apart? I guess I'm planning on running through all the fuel system troubleshooting in the service manual (pressures, vacuum, injector resistance, etc.) before I start pulling stuff off, anything on top of that though?

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    #4
    yes sir,or part failed internaly , oil pump output can be tested with cds
    .................................................. ...the scariest thing in life is the unknown ...................................

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    #5
    Injector resistance won't tell you anything about flow rate, if you have the slightest doubt send your rails and injectors to European Marine (Integrity Injection) for cleaning & verification.
    _______

    Phil
    '09 Hewescraft ProV
    '09 150 Optimax


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    #6
    +1 AGREE
    .................................................. ...the scariest thing in life is the unknown ...................................

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    #7
    Make sure it's worth fixing (cost-wise) before sending the injectors away.
    It looks like this isn't the first time the motor has been apart, imo.

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    #8
    Quote Originally Posted by SilverFox579 View Post
    Injector resistance won't tell you anything about flow rate
    Understood, still a quick/easy check to do. You don't recommend any check for flow rate? Even just checking the spray pattern before shipping them out? I'm not too big on spraying fuel everywhere but would like to know *something* about their current condition before shipping them somewhere.

    Quote Originally Posted by Nova Kaw 650 View Post
    Make sure it's worth fixing (cost-wise) before sending the injectors away.
    It looks like this isn't the first time the motor has been apart, imo.
    You're thinking that because of the difference in cylinder walls? In general though, I hear ya, definitely running through my head and the reason I haven't just ripped everything apart yet.

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    #9
    you can observ fuel inj but what ya gonna do about air inj
    .................................................. ...the scariest thing in life is the unknown ...................................

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    #10
    Quote Originally Posted by andematt View Post
    You're thinking that because of the difference in cylinder walls? In general though, I hear ya, definitely running through my head and the reason I haven't just ripped everything apart yet.
    The cylinders with the cross-hatch pattern look like it was done by hand, rather than machine.

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    #11
    Quote Originally Posted by JOE54 View Post
    you can observ fuel inj but what ya gonna do about air inj
    +1.

    Quote Originally Posted by andematt
    You don't recommend any check for flow rate? Even just checking the spray pattern before shipping them out?
    This is what I recommend, a few minutes on European Marine's injector service page.
    _______

    Phil
    '09 Hewescraft ProV
    '09 150 Optimax


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