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yamaha pro 50hp 1996

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  • yamaha pro 50hp 1996

    Hi, i have just acquired a Yamaha pro 50hp1996 and it is an absolute dog to start.
    It will not start from cold with out a tiny spray of easy start, once running will start first turn of key.
    I changed the spark plugs , and ran it for 20ish minutes, a little rough, and it stalled.
    I took the plugs out again and noticed the cylinder one spark plug had fouling on it (black) and the other two were clean.

    Am i looking at a carb issue or something more sinister within the head, (warn valves, piston rings)
    any help is much appreciated

  • #2
    Have a look on mid carb diaphragm

    1996 P50TLRU Yamaha Outboard CARBURETOR Diagram and Parts

    parts #41


    • #3
      I would say the prime start system is not working properly
      plugged passage maybe or you have the red lever in the wrong position turning it off


      • #4
        hi, just an update to anyone interested, after much deliberation i decided to take the carbs of and give them a clean. ***, i didn't realize carbs could get that dirty, needle valve had to pulled out with pliers on two of the carbs, virtually all the holes were blocked and the gunk in the bottom of the bowls was foul. Anyway cleaned them all up with carb cleaner, reassembled and it started first turn of the key, runs like a dream.
        People always say clean the carbs but i didn't realize the benefits of doing it and it didn't cost anything (apart from carb cleaner)
        Was starting to think i had bought a bit of a dog of an engine but if it did eventually run with the carbs as filthy as they were im thinking it must a pretty good engine.


        • #5
          Start using a fuel stabilizer like Stabil in your gas and drain the carb float chambers(10 MM hex screw on bottom/side of float chamber)a couple of times per year and especially when motor won't be run for several weeks or months.....should eliminate most crud build-up in carbs. My motor is a 1999 and carbs have never been cleaned.....


          • #6
            Or run it often so the fuel in carbs does not have time to evaporate and leave all of that residue


            • #7
              Use marine gas. Period


              • #8
                Originally posted by pstephens46 View Post
                Use marine gas. Period
                Are you talking about gasoline sold by a marina?

                Many feel that gasoline obtained from a high volume regular gas station is preferable to gasoline sold by a marina that might have been sitting around for weeks/months at a time.

                But then some folks let there motors sit for months is not years at a time. I don't care what they do, they are risk of getting a fouled fuel system. Particularly if the fuel system uses carburetors.


                • #9
                  I'd rather let Non-ethanol sit for months as opposed to high volume c-store ethanol.....

                  My small engines have been flawless the past four years with non-ethanol use. Some get used once a week, some get used once a month etc. Before that, many rebuilt carbs and those g-d fuel line replacements.....