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'98 yamaha 90hp alarm

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  • '98 yamaha 90hp alarm

    After running at about 4800-5000 rpms for about 2 miles my motor starts missing and I get a alarm. I didnt hit anything, there is nothing blocking the water intake, and it is "peeing" fine. It acted like a fuel problem (bad gas, trash, water, etc.) but I have never had a alarm for a fuel problem. Its not fuel injected so thats not it. After letting it sit for 5-10 minutes the alarm shuts up and it cranks and runs fine. Would it miss like that when its trying to overheat? Why would it be overheating? Thermastat? Impeller? Water pump? All of the above? Im lost.

  • #2
    saltrookie,
    Your outboard is probably going into rpm reduction mode and the alarm is sounding to tell you the thermo switch has detected an overheat condition.
    There is at least one, maybe two, thermo switches mounted in the head of that 90 Yammie.
    They are designed to close at around 185 degrees to signal an overheat condition to the ignition control. If it has been at least four years since last water pump repair, you probably need to do it.
    I have seen thermo switches falsely close as soon as 130 degrees - giving a false overheat condition signal to the ignition control. You can remove the thermo switch and test in a pan of water, a good thermometer, and an ohmeter.
    Or, you could have a thermostat sticking on you. You can remove it and test like the thermo
    switch.
    You really need a Yamaha shop manual for your particular outboard if you plan on doing any of your maintenance - you are probably looking at a water pump repair. You can get the manual at www.yamahapubs.com and the parts at boats.net.
    Good luck,
    Ken K

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