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Yamaha OX 66 200 HP Questions

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  • Yamaha OX 66 200 HP Questions

    I went out fishing yesterday trolling for stripers, and everybody came back from the fishing trip with an awful headache. If there anything that I can check ?? does the O2 sensor affect the excessive smoke ?? Motor is a 2000 with approximately 150 hours on it. The motor runs great but you can't hardly stand the smell/smoke from the exhaust.Any help would be greatly appreciated.

  • #2
    Re: Yamaha OX 66 200 HP Questions

    lots of things to check. 5 years with 150 hours usually means its a neglected beast. if you look closly at the maint chart its hours or calander WHICHEVER OCCURS FIRST. there are a few things to check, ruptured fuel pump diaphrams will make it run rich, I reccomend new ones wvery 3 years or so, a bad plug cap can make it run rich, excessive fuel pressure can make it run rich. a bad temp sender will also make it run rich. all can be tested but the electrical stuff will require a digital voltmeter and the correct test harness. are there any other symptoms like fuel spots on the water when idling abnormal fuel consumption? also check the oil pump arm for proper clearence and the plastic clip for cracks
    no tech questions by PM, they wont get answered.
    you have to be trusted by the people that you lie to .

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    • #3
      Re: Yamaha OX 66 200 HP Questions

      Originally posted by rodbolt: lots of things to check. 5 years with 150 hours usually means its a neglected beast. if you look closly at the maint chart its hours or calander WHICHEVER OCCURS FIRST. there are a few things to check, ruptured fuel pump diaphrams will make it run rich, I reccomend new ones wvery 3 years or so, a bad plug cap can make it run rich, excessive fuel pressure can make it run rich. a bad temp sender will also make it run rich. all can be tested but the electrical stuff will require a digital voltmeter and the correct test harness. are there any other symptoms like fuel spots on the water when idling abnormal fuel consumption? also check the oil pump arm for proper clearence and the plastic clip for cracks

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      • #4
        Re: Yamaha OX 66 200 HP Questions

        rodbolt thanks for the info. today i did check the spark plug caps and they were in spec. going to try to check o2 sensor is thier a way i could make up a harness to check the o2 sensor? i did replace the fuel pumps 1 year ago. thanks steffysdad.

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        • #5
          Re: Yamaha OX 66 200 HP Questions

          I guess but without the correct size pins its hard, the harness is not expensive.
          no tech questions by PM, they wont get answered.
          you have to be trusted by the people that you lie to .

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          • #6
            Re: Yamaha OX 66 200 HP Questions

            steffysdad, I could not get a harness locally and I was pressed for time so I soldered 2 test leads on the O2 sensor outputs. This works well but the leads need to be waterproofed if you leave them intact. Here is a link that explains O2 sensor operation http://www.boatsetup.com/O2sensor.pdf - but use the testing methods described here and not the torch method for testing. Both my O2 sensors tested bad (2 225's) and replacing them made a huge difference in low speed running and smoke. Although I had other problems as well, the O2 sensor replacement was the biggest change. A few weeks ago we went fishing on a 38 degree morning and I was amazed at the difference in the cold weather running with the new sensors.

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            • #7
              Re: Yamaha OX 66 200 HP Questions

              Centless, how much were your O2 sensors and can they be purchased online.I carried my sensor to the local dealer and they cleaned it free of charge. Used a torch to get it red hot to burn off carbon buildup and a brass wheel to clean tube. Cleaned O2 sensor did nothing to my Smoking motor. 2002 250 Ox66 w/ 300hrs. Runs great on the go WOT getting 4900-5000rpm but idle its smokin and fouling plugs. Thanks for all yalls help been lurking around here for some time......great forum

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              • #8
                Re: Yamaha OX 66 200 HP Questions

                why dont ya do a running voltage output test on the O2 sensor? will confirm or eliminate it as a possible cause. while your at it perform the oil link rod check, most are so far out its not funny. usually I have to clip 5 threads or so off the arm to get the lever to stop pin clearence correct. the bench test for the O2 sensor is a teat on a boar hog. but its time for a general engine check up to include fuel pump diaphrams,o2 sensor outputs and injector leakage tests. 5000 RPM is a bit low, that motor should be propped to 55-56 K.
                no tech questions by PM, they wont get answered.
                you have to be trusted by the people that you lie to .

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                • #9
                  Re: Yamaha OX 66 200 HP Questions

                  rodbolt, the most rpm since new has been around 5200. I thought the same thing but you know dealers, say whatever to get the sale final and out thedoor. Is cleaning the O2 sensor by a torch good enough or does it still need a cleaning solution below the threads. I will look around for a harness to test it out also.

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                  • #10
                    Re: Yamaha OX 66 200 HP Questions

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                    • #11
                      Re: Yamaha OX 66 200 HP Questions

                      ya really cannot clean the sensor itself as its protected behind that metal sheild. its also possible to damage it by overheating it. the only decent test I know is to hook up a DVM to the sensor with the test harness, remove the airbox, and with the gearcase fully submerged in the water,not a barrel. start the engine and allow 5-10 min warm up then while watching the voltmeter cover the top air bypass hoole with your finger. the meter should go something above .8V when the finger is removed it should go to something around .3V then it should start scaling up and down between about .35V to .56V if it does not react or does not scale its bad.also use your DMM to test the plug caps, and check the pump link rod adjust ment per the service manual. if you back off the idle speed screw you will have to reset the TPS voltage but I reccomend checking the TPS output anyway. the lower throttle shutter must be fully closed to check the oil pump lever to stopper clearence, easiest way is to dissconect the lower 2 throttle shafts. most pumps are out of adjustment.
                      no tech questions by PM, they wont get answered.
                      you have to be trusted by the people that you lie to .

                      Comment


                      • #12
                        Re: Yamaha OX 66 200 HP Questions

                        Flipstick, rodbolt's advice is right on --- actually he is the one that walked me through my learning experience. For purchase price... expect to pay in the $250 range. As far as the online availabilty -- there are a lot of options. I hesitate to recommend any one place as so far I have had spotty results ordering online. I purchased my O2 sensors locally as I needed them ASAP and my local dealer came close to the internet pricing. Steffysdad, The more I think of your statement of headaches by everyone, this sounds more like CO2 poisioning than just the annoyance of 2 cycle oil. Are you trolling with your canvass up? For 40 bucks or so I put a 12V CO2 sensor at my helm for that exact concern ... CO2 buildup while trolling in foul weather with the canvass up.

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                        • #13
                          Re: Yamaha OX 66 200 HP Questions

                          Duh --- CO not CO2 ---

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                          • #14
                            Re: Yamaha OX 66 200 HP Questions

                            Well I took my motor in to local shop. They found two fuel pumps that were leaking. TPS was measuring .5??(suppose to be .3 right) Not exacly sure but the mecanic said it was set for 2500rpm. My O2 sensor tested good. Replaced my onboard fuel filter. Oil rod needed adjusting. I think it is idling better now than when it was new.... Thanks Rodbolt

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                            • #15
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                              Re: Yamaha OX 66 200 HP Questions

                              actually I think the TPS setting on that motor is .5v plus or minus .02V. thats with the throttle shutter fully closed and off the idle stop screw. you dont set the TPS for RPM on that motor you set like the service manual says and it works. idle speed in neutral with the gearcase submerged is 730 RPM plus or minus30. timing should be about 5* ATDC at idle and 23*BTDC at wot plus or minus 2* on both settings. timing is controled by the TPS and ECU. see what I mean about the pump diaphrams? did they show them to you ? to close the shutter you can dissconect the top two shutter links or back off the idle stop screw and the linkage sync screws. set the tps to .5V, pink wire to orange wire, do the carb sync then with the gearcase submerged adjust the idle screw to 730 RPM. its also a good idea when checking the TPS to check the 5v reference before adjusting it. to check the 5v reference go orange to red. 5 volts plus or minus .25v.
                              no tech questions by PM, they wont get answered.
                              you have to be trusted by the people that you lie to .

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