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  1. #1
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    Oil Injection Removed L4 2+2

    Just bought a 1994 115 L4 carb motor that had a leaking oil tank. Bought a block off kit and removed entire system. Pulled carbs to rebuild and found out it's a 2+2 system with no idle jets in the bottom two carbs. Is oil delete a no-no on these motors because of the bottom two being "dry" under 1800rpm or whatever it is? Thanks!

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    #2
    I figured it out if someone needs this info. The oil injection pipes into the transfer pump inlet so apparently they aren't real worried about it. I'm gonna run it as is.

  3. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #3
    As you've surmised, switching to premix will not significantly alter the lubrication process of #3 and #4 (just keep in mind that you're quite rich at idle due to the fixed oil ratio).


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
    Still consider myself a "Marine Apprentice" after 46 years (learn something new every day).
    Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor

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    #4
    I didn't know the fuel/oil ratio varied from 50/1 with oil injection. Besides effects on spark plugs and possibly cylinder glazing from excessive idle, is it a bad thing? Should a full fuel burst be run for every "XX" minutes of idle? Thanks Sir. I enjoy reading your posts.

  5. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #5
    Simply avoid excessive idling, try to run the engine up into the 4000+ RPM band near the end of your boating day so as to avoid excessive carbon buildup.

    Also a good idea to run Quickare + Quickleen in each tank of fuel, and high-quality oil (Merc or Quicksilver Premium PLUS would be a good choice).


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
    Still consider myself a "Marine Apprentice" after 46 years (learn something new every day).
    Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor

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    #6
    10-4 I'll try and use the electric more using the StructureScan and trolling. Seems to read best around 3mph. I'm a Lucas guy, for decades. All the boxes in the HO Harley, even fork oil, and all my past race motors and gear boxes. I use semi-syn in the outboard plus a double dose of Startron. I'll bear in mind the 4000+ thing and try to prop it as close to the 5250 top side that I can. It's got a Laser II 19p on it now but will have a Trophy+ when I narrow down the pitch for 5250. Carbs an intake on the bench right now for a cleaning and CCMS reeds, but I'll have it going again mid-week. It wouldn't idle well cold; starving out. Thanks again Sir, and Merry Christmas.

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    #7
    Let us know how much the new reeds help the idle quality.

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    #8
    Will do sir, but the carbs were purdy contaminated so my "base line" is skewed. Bought the motor used last year and just got it hung end of last month.

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    #9
    IMG_3146 (002).jpgIMG_3145 (002).jpg
    If anyone is interested, L3/L4 Merc's have about 15% more intake air available with a couple hours work.
    Untouched reed cage...

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    #10
    IMG_3151 (002).jpgIMG_3152 (002).jpgIMG_3148 (002).jpg
    Cleaned up cages and the 600 grit wed/dry with carb cleaner used to lap the faces. That's always a good idea even if you don't port em.

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    #11
    IMG_3149 (002).jpgIMG_3150 (002).jpgIMG_3153 (002).jpgIMG_3154 (002).jpg
    The intake holds the most to gain. The third pic shows how much "plenum" opens up with a little grinding. The last pic with the cage offset shows how much material covers the outside of the reed, where the most air is. More than 15%.

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    #12
    IMG_3155 (002).jpg
    Ready for assembly.

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    #13
    I'm in for this! Looking good....👍

    I have the same engine....'95 115....took a bit of work (and about a grand) to get it back into good shape, primarily the idle (having flashbacks...😉). She's running like a top now and surprisingly powerful, etc.

  14. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #14
    Just out of curiousity- how are you planning to provide additional fuel to compensate for the modified airflow?


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
    Still consider myself a "Marine Apprentice" after 46 years (learn something new every day).
    Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor

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    #15
    Freeing up the blocked air at the intake, tho the coverage of the holes is almost a whole third, doesn't actually equate to that percentage of air in the ratio as to the carb throats, cylinder ports and tuner/exhaust are all still the same. Because of that, stochiometric efficiency doesn't really change measurably either. Really doubt a sniffer would read it. Intake and tuner/cavity work would change it, but as compression can't be modded it's still not that much. Nothing I've ever seen done to a Merc L motor, including cylinder port work has ever been substantial enuf to warrant changing carbs. Plus, the L3 90 I had was fine as is with an idle adjust on the bottom two, but had a great hole shot. Top carb didn't change at all. This is my first personally owned 2+2 tho. Great question sir.

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    #16
    Quote Originally Posted by EuropeanAM View Post
    Just out of curiousity- how are you planning to provide additional fuel to compensate for the modified airflow?
    I feel rather stupid now having read your sig for the first time this morning. Now I think I shoulda just asked you for your recommendations...

  17. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #17
    Good idea to perform a couple of plug-reads after running at 4000 RPM's, and then at WOT RPM's (assuming plug read at 4000 RPM's looks ok).

    I'll admit to having done some "cleanup" of my own engines (and those I've built)- though nothing nearly this aggressive.

    Good luck!


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
    Still consider myself a "Marine Apprentice" after 46 years (learn something new every day).
    Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor

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    #18
    Motor idles perfectly now. Purdy sure it's a combination of tight seals at the reeds and very clean carbs (used jet files and cleaned everything out very well). One enricher pump and it fires right off cold, then it's turn key and pops right off the whole rest of the day. Holeshot and top end performance are as expected. Again, no real baseline from before to after as top end was hindered by jet contamination, but prop blow-out is ridiculous now. Time to fine tune the prop set-up, and add power steering. Motor torq on single cable steering is almost uncontrollably stupid now.

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    #19
    good choice for power steering as most aspiring marine techs are misled that regular hydrolic steering will NOT eliminate torque , engine setup and propeller choice can and will make a greater difference on most all boats as well as no feed back or dual cable setup , power steering is quite pricey also, good luck ....... JOE
    .................................................. ...the scariest thing in life is the unknown ...................................