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    engine ID

    The Yamaha C and CV models did not come with oil injection.
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    Starting Issues - 9.9 HP Mercury OB

    What is the model of the motor? 9.9's are not all the same.
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    engine ID

    I am guessing 1987. Similar to a Yamaha CV40 or C40 model. Take a look at the carburetors and the CDI assembly. See what markings you find on them. I am guessing 6E9 XX for the carburetors and 689 for the CDI assembly. Take a look at the Yamaha parts catalog for their CV40ELD model and see if...
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    OEM digital gauges for 1999 115 Yamaha

    www.gaugesaver.com
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    2006 Mercury 9.9 ignition coil burned up

    Not common but not unheard of. The coils mounted under the flywheel live a harsh life.
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    95 Mariner 4 stroke 9.9

    See post #7.
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    95 Mariner 4 stroke 9.9

    Was the Primestart device removed from the carburetor? When cold the pin should be retracted. Applying 12 DC volts will cause the pin to extend but it takes time. Minutes. Slowly. It does not happen quickly.
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    CDI High Speed Failure

    How many charge coils in the model? If it uses low speed and high speed charge coils it might just be the high speed charge coil that has failed.
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    CDI High Speed Failure

    The best quality stuff in the world have have an earlier than expected failure. On the other hand, cheap stuff can last far beyond its expected lifetime. Just the way that it goes.
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    97 40hp Merc serial number isn't matching up with it's parts?

    Well now you know. This is how we learn.
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    97 40hp Merc serial number isn't matching up with it's parts?

    Why not use the www.mercurypartsexpress.com website?
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    Need help

    Any idea as to the model of the motor?
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    '99 115 Yamaha choke butterfly plates are different

    Choke plates restrict the flow of air so as to increase the flow of fuel. Some have holes and some don't. I can't imagine the two different sized holes being a mistake. I am just guessing as to why they are different. But if if it is a manufacturing mistake then I will not argue against it.
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    '99 115 Yamaha choke butterfly plates are different

    Oops. You are correct.
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    '99 115 Yamaha choke butterfly plates are different

    Formula for the area of a circle is pi X r squared. Area of a 1/8" diameter circle is 0.012272 Area of a 1/2" diameter circle is 0.019635 The area of the larger hole is not even twice the area of the smaller hole. Not 5 times as large. Your first post said the choke plates with the smaller...
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    '99 115 Yamaha choke butterfly plates are different

    Depending upon their position I can see one set of carburetors allowing more or less fuel to flow. Which is why some carburetors use different idle and main jets. The carburetors with the smaller choke plate holes must need a bit more help drawing fuel into the carburetor when it is cold.
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    1999 Yamaha 115 idle adjustment

    The motor itself does not have an electric fuel pump. Or anything on the motor that would make a noise at key on. Perhaps someone added an electric fuel pump in the boat. Follow the fuel hose from the motor to the tank. See what is to be seen.
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    Low Compression, Low $ Advice

    There is a benefit to running pig rich. Less chance of leaning out a cylinder. Better to have rings with carbon build up than a seized piston.
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    High Pressure Pump OX66

    Having no idea which OX66 model you have, I cannot check to see what a Yamaha service manual says the pressure should be.
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    High Pressure Pump OX66

    The fuel pressure will vary. As a function of engine manifold pressure. Highest pressure at key on, engine off. A different pressure when the motor is running but at an idle. As the throttle is opened up the fuel pressure should go up. Throttle retarded the fuel pressure should come down.
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