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Thread: 40H carbs?

  1. #1
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    Default 40H carbs?

    Cleaning up the carbs on my 40H . Found a drilled hole on the port side,after the throttle plat,about 1/2" behind the last progression hole.Carbs are AJ33A.
    It is on both carbs. The amount of dirt on the carbs I never saw it.
    This is a direct leak in atmosphere? Is this a "H" thing?or does this need a plug?
    Thanks of the help! Can't find anything in the manual!
    Randy

    Added a photo. Hole is just ahead of the mounting flange.

  2. #2
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    Seen that before. I believe its purpose is to raise the idle speed/ air flow rate at closed throttle.

    On Merc triples, I've found that enlarging the three, existing holes in the butterfly to 1/8 " makes a HUGE difference in eliminating bogging. The enlargement is not that much, but the effect is impressive! Perhaps that's another reason for that hole?

    Jeff
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    Thanks Jeff. That is what I was thinking . May have something to do with the H lower unit? Can't seem to find a idle RPS in the manual. Not mush info in the manual for the 40H

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    Sam Cullis Mark75H's Avatar
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    Doesn't have anything to do with the lower unit.
    Since 1925, about 150 different racing outboards have been made.


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    I was thinking that Q lower mite need a higher idle? That's all.

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    Sam Cullis Mark75H's Avatar
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    Nope, generally doesn't. A few years later all racing motors were altered to stop at low idle rather than idle well as a safety measure. I have no idea what the holes are really for or if they would be found on all
    Since 1925, about 150 different racing outboards have been made.


  7. #7
    Administrator Ron Hill's Avatar
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    Default If It Means Anything

    My dad probably rebuilt every Mark 40-H in SoCal.....Like maybe 6-8 total. I used to take things like the carbs off, port covers off, and the belt on the mag off. At 10 years of age or so, I saw almost everything on a motor. Had the Mark 40-H had holes drilled in the carbs, I would have seen them. I never saw holes like this.

    Around, 1958, we had a Mark 40, "Club Foot" that we ran on an old C Runabout (Morehouse) that Ken Scoville had owned. We threw a rod through the block at Blythe one New Years, that motor didn't have this hole in the carbs, I know for sure.

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    Administrator Aeroliner's Avatar
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    Default Carbs

    I will look at the two 40-H engines I have. I beleive that was a normal feature. I will also check my 40-H parts manual.

    Alan

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    Thanks Ron. I would say it looks to have been their from new,but???
    Carbs are missing the long low speed valve? Has shorts now?
    Now sure if you are the same person that built props for my Schiada Sea's B85,but best props I had till they hit a shark. Oh well!

    Alan,thanks for taking a looking . I guess I will know what they do when I get the power head running.

  10. #10
    Administrator Ron Hill's Avatar
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    Default Well, I Was Thinking

    Maybe, at ten years of age, I over looked the hole.

    Did KG-4-7 carbs have this hole???

    Fun thread here, anyway!

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