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1996 Yamaha C150TLRU 2 stroke outboard will not idle when trimmed up

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  • 1996 Yamaha C150TLRU 2 stroke outboard will not idle when trimmed up

    I recently purchased a hurricane 206 deck boat with a 1996 Yamaha C150TLRU outboard, carb model, it has 3 dual carbs on it.

    I took the carbs off to clean them, i removed all the jets, blew compressed air though all the jet/pilot holes and passages, everything was clean and is clean.
    only thing wrong that i found in the carbs was the float drop levels were totally random and off from the 16mm spec, so i set all the floats to 16mm without gasket per service manual.

    The problem i am having is the motor only wants to reliably start and reliably idle when it is trimmed all the way down.

    if i trim the motor up, not all the way up to the point the prop is out of the water, but a normal shallow water amount of trim, and idle in gear into a shallow dock, the motor will start shaking and stall within 20-30 seconds of being trimmed up.

    if i give it gas and keep the rpms higher while trimmed up, say 1200+, it will keep running fine.

    I cant wrap my mind around what can be causing the motor to idle perfect when trimmed all the way down, and stall in idle when trimmed up?

  • #2
    Float level ?


    • #3
      Originally posted by Keithbaja View Post
      Float level ?
      Set to 16mm per fsm


      • #4
        ok, problem solved.
        Not sure exactly what fixed it, as i fixed a few different things at the same time.

        replaced fuel/water separator
        replaced fuel hoses leading to carbs, made sure no more fuel vacuum leaks (i think this was the biggest issue)
        set the carb fuel floats correctly this time 16mm with gasket, per FSM
        removed fuel filter cartridge on the side of the engine, it had a lot of beige looking caked gunk inside. ordered a new one to replace it.

        engine runs great now, winds to 5100 rpm, 37mph and does not stall, no matter the trim angle.