1996 25 hp merc problems

Discussion in 'Outboard Maintenance' started by jlutsey, Sep 24, 2010.

  1. jlutsey

    jlutsey I Love microskiff.com!

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    Hey Guys,
    first time poster here hoping to get a little help from the experts. Here's the story...resurrected a 1996 25 merc the other day that has been sitting for about three years. cleaned the carbs well, changed plugs, water pump, thermostat, foot oil, and new gas. I ran a can of mercury power tune and thoroughly cleaned everyhting i could get to.

    The motor will cran pretty easily when cold and will run like a scalded dog at mid to WOT but idles and slow trolls very rough if at all. There is significant hesitation on the acceleration but it flys when WOT. If it cuts off whe its warm, it takes forever to get it restarted, seems like its flooding. When i do try to crank it, it gets closer to running every time untl it finally fires, then smokes and shakes and sputters.
    all of the proble,s seems to be on the low end.
    Would replacing the reeds and cage help, Low speed jet bad?

    I know it's a long shot, but any help is greatly appreciated!
    thanks
     
  2. Gramps

    Gramps Living & Dying in 3/4 Time

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    Did you adjust the low speed idle jet screw? It sounds it is not letting enough fuel in at idle / slow speed.  Try turning the idle screw in slowly to bottom out, turn out 2 turns and then start the motor.  Slowly turn in until it spits & sputters, note how many turns from your "zero" point, return to "zero (2 turns out). And then turn out until it sputters again.  Average the turns from "zero", adjust the screw to that measurement and see if that helps.

    Hopefully I didn't tell you something you already tried!  ;)  Good luck!
     

  3. jlutsey

    jlutsey I Love microskiff.com!

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    is that the screw that you access through the plastic cover on the front of the carb? i thought it was the air adjustment..
     
  4. Gramps

    Gramps Living & Dying in 3/4 Time

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  5. jlutsey

    jlutsey I Love microskiff.com!

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    ok, i was working with that earlier and got me to the point that it will run. Perhaps more adjustment is needed. Any ideas on the sluggish acceleration?
     
  6. Gramps

    Gramps Living & Dying in 3/4 Time

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    If it isn't fixed by the low speed jet, it's out of my realm. There should be some more knowledgeable folks around soon to help out.
     
  7. Brett

    Brett > PRO STAFF <

    I'm thinking you didn't get the low speed passages completely clean.
    The least bit of dirt or varnish in those small diameter feeds
    will prevent you from obtaining a smooth running engine.
     
  8. Swamp

    Swamp I Love microskiff.com!

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    I had let my Johnson 25 sit for a couple of years when I moved over here from the east coast because of lack of time to fish. Had the same issue. I just had to run it. It just cleaned up more and more, after half a dozen trips you just could not tell anymore. Kinda sucked because I had to idle out to the channel, and that is exactly what it did NOT want to do. Just put the beans to it for a while, maybe take the dog for a nice long boat ride.

    Swamp
     
  9. jlutsey

    jlutsey I Love microskiff.com!

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    would running some carb cleaner in the fuel help?
     
  10. Gramps

    Gramps Living &amp; Dying in 3/4 Time

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    Seafoam is an option!
     
  11. Swamp

    Swamp I Love microskiff.com!

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    Just don't over do it, these small engines can be sensitive. Meaning if 2 oz. is good don't add 4 oz (just to pull numbers out of the air). Seafoam is a reputable product. You may also want to soak your carb(s) in cleaner over night to dissovle any varnish etc. just be sure you have removed all plastics and rubber.