Re: 1974 Evinrude 9.9 won’t idle at low RPMs, need help

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April 24, 2016 at 4:11 pm #35390
hotpickle
Participant
    quote pugetsoundboater:

    A compression test will give you a good idea of what condition the motor is in. Look for at least 80 Psi,after 5 pulls of the starter cord. Pull that cord like you mean it, both plugs out.
    The carb low speed needle should be set at 1 1/4 turns out counter clockwise, after turning it in clockwise all the way to lightly seated ,not forced closed all the way,that’s your starting point.
    Do you have fresh gas at the proper 50:1 ratio? Did you start with a clean tank and hose,no water in the tank ?
    Looks like it’s smoking a bit , should be able to run without the choke .
    Feel the top of the motor,the flat spot right above the cylinder head. Is it warm? It should be quite warm ,if not your thermostat is stuck open or missing.
    Our experts here will chime in with a lot more tips,and welcome to the forums.

    The fuel is a couple months old, 91 octane. I also have an old metal gas can without a vent so i crack the lid (it is definitely the original gas tank, its super old). I have recently read that 87 Octane is recommended for my motor, so my plan for next weekend was to get a new, cleaner gas tank with a proper vent and some fresh 87 Octane. Would it be a good idea to replace the spark plugs, since they took a good cleaning when i took them off yesterday? I had read that you had to use a slightly hotter spark plug with this motor for better firing at lower rpm/idling (the original spark plug is apparently out of production). The part number that has been given is NGK BR6HS, can anyone confirm this? I didn’t think to check on this when I had it apart yesterday and see if I had the right spark plugs. But it starts up pretty quickly so i figured it wasn’t the spark plugs.

    Every time i push the choke in all the way, it sputters out and dies (makes a backfiring noise). I tried to counter this with the idle adjustment, and i got it to run pretty smooth at 1/4 choke (before i played with this, it ran smoothest at half choke), but it still peters out when i try to take the choke all the way off.

    I did feel the top of the motor. It was warm, but not uncomfortable to the touch. I had read that this was a sign the water pump was working because there is no telltale? Also, as the motor warmed up, more water came out the exhaust hole on the back, which I had also read was a good thing.