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Thread: 25 hp mercury

  1. #1
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    Default 25 hp mercury


    I need help I have a 25 hp 2 stroke outboard that i cant get to idle. i have rebuilt carb, fuel pump, put on new coils plug wires ect. It shacks be low about 1400 rpm in and out of gear. will the 2 rubber horses from behind carb that go to intake side cylinder's cause this problem it has 100 psi in both cylinders.

    Randy

  2. #2
    Barnacle Bill's Avatar
    Barnacle Bill is offline Super Mod and 2014 Crappie.com Man of the Year * Crappie.com Supporter
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    Have you got a strong spark at both plugs. Those older 25 Mercs are notorious for squirely acting switch boxes
    Fair Winds and Following Seas

    Bill H. PTC USN Ret
    Chesapeake, Va


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    Thanks for that info

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    I'll help walk you through the most likely causes but I have to ask that you proof read your spell check and post your results of what the problem was.
    I'd rather be fishing.

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    The most likely cause is in the carb. You mentioned that you cleaned it. The carb bowl has an 11mm (7/16) brass cap on the bottom. It has a spring and ball under it. If the ball is missing or has been shoved down into the spring, the engine is receiving too much fuel and can't digest the extra fuel at anywhere near idle speed. Remove carb and check that first
    I'd rather be fishing.

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    I will do that tomorrow I got motor off boat and in 55 gallon test barrel Thanks for your help

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    Sliderman I took off carb and unscrew brass plug It holds fuel bowl on carb. There is no spring or ball all i see is the fuel jet

    Randy

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    Wrong cap. That one is 13mm/1/2 inch. The one you need to check is beside it. Give me a year model guestimate.
    I'd rather be fishing.

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    Its a 1988 25 hp mercury

  10. #10
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    Ok. Check the smaller brass cap that sits beside the main jet. The ball should be at the bottom with the carb upside down.
    I'd rather be fishing.

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