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F90 - cdi burnt up!!

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  • F90 - cdi burnt up!!

    Hey there!
    Bad mother's day for CatCam -

    Took my 2004 90HP FFour Stroke out today and noticed a few things that were not quite right before the magic blue smoke came out of the CDI.

    I noticed on my Yamaha Digital Speedometer that my Voltage would run up to 16.4 Volts when running high speed.....then I had a rough idle, I had to use the throttle lever to keep the engine from killing. I put the boat in idle and got the burnt smell of electronics - NOT GOOD.

    I headed back to the dock, got the boat home - pulled the cowling off and the breather cover -- There was the burnt CDI - so bad that some of the melted material fell on the Voltage Rectifier. Damn.

    So, besides the obvious that I'll be out a cool $1K what does Yamaha Forum Think? What would cause this?

  • #2
    your first clue was the over volt.
    most likly it was the regulator overheated then smoked the CDI.
    usually regulator failures get traced back to loose wing nuts on the battery terminals.


    • #3
      I will ensure the battery wing nuts are tight - battery voltage is 13.1V, so this looks good.

      I'm going to go ahead and change the Rectifier/Regulator Assembly ($187.59)and the CDI ($361.66) - Yeah, it hurts but I cannot do without my boat!

      BTW - the motor still ran fine at high speeds just the idle was all FUBAR'd! I can say that my Yamaha has never left me stranded!

      Is there anything else I should check?
      Is there anything else that would cause the CDI to melt?


      • #4
        Throw away the battery wing nuts and use stainless steel nuts and lockwashers tightened with a wrench.


        • #5
          Originally posted by seahorse5 View Post
          Throw away the battery wing nuts and use stainless steel nuts and lockwashers tightened with a wrench.
          I will heed this warning!! If this was the root cause it is a lesson learned (the expensive way!)

          Is there anything else I should check?
          Is there anything else that would cause the CDI to melt and or regulator/rectifier to south?


          • #6
            I got my new CDI and Voltage regulator for -- a lot cheaper than my local dealer. This weekend I'm going to change them out.

            Friend of mine has a 115 and his voltage regulator went out....but didn't burn up the CDI so I guess he lucked out.

            It seems both parts have been superceeded by new ones.....hopefully Yamaha made them more robust......

            I'll post back with results!


            • #7
              Motor is FIXED!

              The root cause:

              2 years ago I dropped my carbs and cleaned them. When I reinstalled the carbs I pinched the blue wire from the Prime Start Assembly.
              When I put the carbs back on my digital tach would only give me a "0" reading when the engine was running. I measured output from the CDI and got some garbage readings so I figured my CDI was on the blink.
              To get a tach reading I jumped a wire from my voltage regulator (green wire) directly to my tach.

              All was well, but from time to time my Digital Sppedometer would give me a flashing 16.4V - 16.6V reading. I also had some problems with low idle and rough low speed operation.

              Fast forward to mother's day when all hell broke loose and it looked as if the CDI fried.

              I ordered a new CDI and Voltage Regulator for and we installed them yesterday....motor ran okay BUT I was not getting any tach reading.....

              Then we found the pinched wire - almost severed with some corrosion! So I did the splice repair and BAM! Tach started working! Rough idle is GONE!

              20/20 hindsight is that the voltage from this wire was running into the engine block, causing grounding problems, thus making my voltage regulator BURN (yes burn). Didn't realize how bad the Regulator was until I removed it. ***, bad. So bad I think the HEAT from it actually burned the CDI unit.

              Ran the boat for 6 hours today with NO problems! Voltage is now between 13.5V- 14.4V depending on my RPM.

              Life is Good again!


              • #8
                hard lesson and rather expensive.
                I will double check your wiring diagram, something in your description does not sound right.
                however this morning I am in caracas VE trying to use a spanish keyboard.