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Is This a Reed Valves problem in 85 Merc 75 hp Outboard

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  • Is This a Reed Valves problem in 85 Merc 75 hp Outboard

    What are reed valves in my 85 Mercury 75 hp outboard and how hard are they to replace. If reed valves were damaged how could that happen and and what would the effects of damaged reed valves be? My motor runs good when you first get in the water but after the motor warms up when you stop and then engage gear again it wants to stall or bog. I can still get it to go by playing with throttle and I can hit choke while giving it the gas and it takes right off. Cranks every time and runs smooth in idile and runs great at speed just problem taking off. Compression is good also, can run all I want as long as I keep moderate speed no prob. just on take off , does this sound like reed valves problem?


  • #2
    Re: Is This a Reed Valves problem in 85 Merc 75 hp Outboard

    No, it is not the reeds, they are one-way flapper style air valves in the intake that prevent the intake charge from blowing back out the carb while the piston is on its down-stroke.

    Poor acceleration + good idle (seemingly) + good top end = is usually a problem in the idle circuit of the carb, getting dirty and not flowing enough fuel.

    You could try backing out the idle mixture screws just the width of the screwdriver slot, but it would be better to properly clean the carbs as you can't know what else may be getting restricted and you do NOT want to run your motor lean, that will melt pistons and spoil your whole weekend.

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    • #3
      Re: Is This a Reed Valves problem in 85 Merc 75 hp Outboard

      Thanks for the advice CharlieB, glad to hear that this is not a REED VALVE problem.

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      • #4
        Re: Is This a Reed Valves problem in 85 Merc 75 hp Outboard

        Riverknight, For future reference. A symptom of bad reed valves is gas pouring out your carb from leaking back-cylinder pressure.
        The dictionary is the only place that success comes before work.

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        • #5
          Re: Is This a Reed Valves problem in 85 Merc 75 hp Outboard

          Thanks WingedWheel , I appreciate the info, this is a great site and any information I aquire in the future I'll be sure to post so I can hopefully help someone.

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          • #6
            Re: Is This a Reed Valves problem in 85 Merc 75 hp Outboard

            Another symptom I learned the long hard way is hard starting. This was on an old Johnson V-175.
            '90 Donzi GT230-5.8 Cobra. '77 Scarab Sport 30-twin 200 Black Max.

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            • #7
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              Re: Is This a Reed Valves problem in 85 Merc 75 hp Outboard

              OK , Marine Service Center called , said they found the problem , said it is the carbs and they doing a carb rebuild on my 85 Mercury 75 hp , supposed to get it back Monday then I'll know for sure , hoping they got to the bottom of this...lol... but I can't be sure till it's back in my hands if you know what I mean..One thing I can tell you if they do got it right it's better to just take your boat to the top Service Center you can and forget the cheap way out cause they never get it right.

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