1991 yamaha outboard problem
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Thread: 1991 yamaha outboard problem

  1. #1
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    Default 1991 yamaha outboard problem

    Im having problems with my 150 yamaha and i can not figure what is wrong with it. The rpms will start jumping between 2100 and 2500 rpms the alarms will start going off. Ill put the boat in neutral and it stops and the boat will run fine for the rest of the day. Sometimes this will go on for an hour. It always seems to stop and the boat will run fine. Im leaning towards having to replace the cdi unit but iwanted to see firts if anyone else has ever had a similiar problem and how they fixed before i go ahead and replace it.

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  3. #2
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    Sounds like the low oil safety. When the oil gets low in the two stroke oil reservoir the rpm's automatically drops into the 2000 to 2500 rpm range and the alarm sounds. Even if you have a full reservoir the safety may be engaging.

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    Quote Originally Posted by jake2831 View Post
    Im having problems with my 150 yamaha and i can not figure what is wrong with it. The rpms will start jumping between 2100 and 2500 rpms the alarms will start going off. Ill put the boat in neutral and it stops and the boat will run fine for the rest of the day. Sometimes this will go on for an hour. It always seems to stop and the boat will run fine. Im leaning towards having to replace the cdi unit but iwanted to see firts if anyone else has ever had a similiar problem and how they fixed before i go ahead and replace it.
    Trust me, you don't want to buy a new powerpac for that engine and it doesn't sound like you need it.

    What alarm goes off. Is it steady or intermittant? Have you pulled the engine cover to check the oil level in the oil tank on the engine. Has the oil tank in the boat been serviced lately. Yams have the oil pump in the tank in the boat.

    When did she have a water pump, tstats and the popet valve serviced last?

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    the alarm is steady oil levels are fine i replaced water pumps and thermostats in the spring. The rpms will just go up n down between 2000 and 2500. Once i drop the throttle below 2000 the engine runs fine and as soon but the alarms are still going off. i just wait a little bit and the engines run like theres nothing wrong.

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    Quote Originally Posted by jake2831 View Post
    the alarm is steady oil levels are fine i replaced water pumps and thermostats in the spring. The rpms will just go up n down between 2000 and 2500. Once i drop the throttle below 2000 the engine runs fine and as soon but the alarms are still going off. i just wait a little bit and the engines run like theres nothing wrong.
    A steady alarm is heat. Did you service the popet valve? It's on the back of the engine bottom port side under the coils. Yam calls them a water pressure relief valve. Over 2000rpm pump pressure pushes it open to let water free flow thru the engine. If they hang open the engine will overheat because water will drain out of the powerhead fater than the pump will fill it. If they stick closed you'll overheat around 2000-2500+ rpms.

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    Dunk...thats what I would say it is.... Happened on mine. Pretty easy fiix to.

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    Some Yamahas also have a steady alarm for low voltage in the circuitry.

    Usually you will find loose or corroded connections somewhere or sometimes the boat wiring harness from the engine to the keyswitch has green corrosion growing inside the B+ or the yellow wires.

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    is the only thing the alarm can be is overheating? Also when its jumping between 2000 and 2500 it sounds like the engine isnt running on all 6 cylinders

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    Quote Originally Posted by jake2831 View Post
    is the only thing the alarm can be is overheating? Also when its jumping between 2000 and 2500 it sounds like the engine isnt running on all 6 cylinders
    Check your wires and coils too. My friend has a 1993 175 Yammie and has had to replace a few coils. He didnt have any alarms going of, but definately lost power intermittantly. I am not sure if the insulation on the wires allows arcing or what, but that solved his problem.
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