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2003 yamaha 115 4 stroke bogs down, misses badly above idle

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  • 2003 yamaha 115 4 stroke bogs down, misses badly above idle

    Long story short, took boat out, ran perfect up to 4200 rpm, but no higher, suspected old gas. Ran a couple hours at 4000 rpm, tooled around for a half day at various speeds, start and stop, ran the same. Started up to come back in and couldn't get on plane. Added some new gas, no change. Would start and idle fine, run up to 3000 then start missing and bog down to 2500. Babied it back in, dropping the rpms down until it ran smooth, only turning 1500 when I got in. Changed all filters, cleaned VST and entire fuel system. Screen in VST was 2/3 clogged with trash but rest of system was clean. Changed plugs, 3 and 4 were gas fouled. Now getting 36 to 44 psi at the fuel rail with all injectors working. Resistance on coils is in spec, TPS voltage is perfect. Source voltage to coils never gets above battery voltage (12 to 13 volts), checked with a digital multi-meter. I suspect stator coil, but want to nail-down the problem(s) before buying parts. Is there any way to check the stator coil? What else should I be checking?

    Any info will be greatly appreciated, Thanks!

  • #2
    Re: 2003 yamaha 115 4 stroke bogs down, misses badly above idle

    I would do a leak down test to make sure cylinders are sealing properly to start out with, I am not sure how the 4 stokes hold up when running lean, but it is always a good idea to make sure the motor is in good shape before chasing things around.

    Testing ignition system has to be done with a peak reading voltmeter made for these systems or use a DVA adapter and a regular meter.
    a Yamaha service manual for your motor will give step by step procedures and the specs for tests

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    • #3
      Re: 2003 yamaha 115 4 stroke bogs down, misses badly above idle

      I have to order some more tools, will post what I find-out.

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      • #4
        Re: 2003 yamaha 115 4 stroke bogs down, misses badly above idle

        Originally posted by ChrisWilliams View Post
        Now getting 36 to 44 psi at the fuel rail with all injectors working.
        How did you check the injectors?
        Did you send them out for flow testing and cleaning?
        They (injectors) still could be the culprit if you didn't test them properly
        "Somebody put salt in the ocean to punish us boaters"
        1989 22' Bayrunner Cuddy (Aluminum)
        2002 Merc. 115 Saltwater Series Fourstroke
        1988 Yam. 9.9 High Thrust Fourstroke
        1998 Dodge 2500/ 24V. Cummins diesel

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        • #5
          Re: 2003 yamaha 115 4 stroke bogs down, misses badly above idle

          Hi, I have a 2005 150 hrs with very similar problems that no one can fix.
          Did you find the issue and fix yours? Anything would be helpful and appreciated.
          Thanks

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          • #6
            Re: 2003 yamaha 115 4 stroke bogs down, misses badly above idle

            Originally posted by ChrisWilliams View Post
            Long story short, took boat out, ran perfect up to 4200 rpm, but no higher, suspected old gas. Ran a couple hours at 4000 rpm, tooled around for a half day at various speeds, start and stop, ran the same. Started up to come back in and couldn't get on plane. Added some new gas, no change. Would start and idle fine, run up to 3000 then start missing and bog down to 2500. Babied it back in, dropping the rpms down until it ran smooth, only turning 1500 when I got in. Changed all filters, cleaned VST and entire fuel system. Screen in VST was 2/3 clogged with trash but rest of system was clean. Changed plugs, 3 and 4 were gas fouled. Now getting 36 to 44 psi at the fuel rail with all injectors working. Resistance on coils is in spec, TPS voltage is perfect. Source voltage to coils never gets above battery voltage (12 to 13 volts), checked with a digital multi-meter. I suspect stator coil, but want to nail-down the problem(s) before buying parts. Is there any way to check the stator coil? What else should I be checking?

            Any info will be greatly appreciated, Thanks!
            Hi; I live in David,Panama and I'm having the same problem with my 2005 yamaha 200hp ,so if you find the problem before me please post it.Its hard to find some one here to work on one that good Yamaha dose not have one. THANK YOU

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            • #7
              Re: 2003 yamaha 115 4 stroke bogs down, misses badly above idle

              Perhaps I can help you.
              First of all, when you start up engine, does it crank immediately or after running starter 2s or 3 s ?
              If it cranks after 2s or 3s, you have a code error.
              Depends of your answer, I could tell you what to do.

              Comment


              • #8
                Re: 2003 yamaha 115 4 stroke bogs down, misses badly above idle

                It starts within the first 2 or 3 cranks.
                I have not error codes from the engine and it all checks out good according to dealer, they blamed fuel. I changed all fuel and installe water fuel serpeator, still have the issues. Only revs to 4200 RMP and 35 MPH instead of 5200 and 47 mph. If I pump throttle it goes to 4500 and 39 mph for a short time.
                I have VST filiter but didn't change as I have 38 PSI at injector rack. Clean injectors I think? How? Other ideas?

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                • #9
                  Re: 2003 yamaha 115 4 stroke bogs down, misses badly above idle

                  I have had this problem a couple times Thank god for Yamaha's extended warranty. Your injectors are clogged. I have had the injectors cleaned and replaced a couple of times. turns out the cause of this is the ethanol attacking the materials in the VST filter housing. I replaced the housing , the VST filter and the injectors and it has been doing well since. After you do this try to run ethanol free gas if you can and keep the tank full to help prevent condensation build up getting into the engine.

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                  • #10
                    Re: 2003 yamaha 115 4 stroke bogs down, misses badly above idle

                    I made a DIY injector cleaner I saw on Youtube, ya I know crazy.. but when you have no support you have to try things.. I shot the carb cleaner straight through the injectors while cycling them and my engine ran better than it has for a year.. Got the missing 1000 RMP back..,, still hesitates and not totally 100% but way better. Prob still needs VST filter change and a another clean or profession rebuild of injectors, but the injetors are definitly my issue.

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                    • #11
                      Re: 2003 yamaha 115 4 stroke bogs down, misses badly above idle

                      After verifying engine condition, I would pull this hose off and squeeze the primer bulb. If fuel comes out of this fitting that means that the needle in the VST is being held open by some sort of debris and is leaking into the intake by way of regulator hose. If this is clear and the VST is holding pressure I would drain the VST when you experience the probem into a graduated cylinder record the reading then squeeze bulb until light pressure is felt and drain again into same container. Compare readings if reading is significantly less you have a possible fuel restriction.
                      DO YOU HAVE: GOOD COMPRESSION, PROPERLY TIMED SPARK, PROPER FUEL AIR MIXTURE?

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                      • #12
                        Re: 2003 yamaha 115 4 stroke bogs down, misses badly above idle

                        why not simply monitor fuel rail pressure?
                        if rail pressure is ok and it wont turn up then send off the injectors.
                        thars.
                        t F115 uses a 12V waste spark TCI ign.
                        lose a pulser coil and it defaults to fixed timiming and you will never see anything close the 4200 RPM.
                        the rest of the engines on this post are worthless posts as we dont know what system is used.
                        no model numbe
                        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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                        • #13
                          Re: 2003 yamaha 115 4 stroke bogs down, misses badly above idle

                          Same problem with 2005 F150. Fuel injectors and fuel system cruded up due to ethanol. Low fuel pressure and plugged injectors. What is best additive for gas with ethanol?

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                          • #14
                            Re: 2003 yamaha 115 4 stroke bogs down, misses badly above idle

                            Their is no additive to help counter the effects of ethanol. You may be saying wait a tic, Stabil has ethanol treatment. No OEM manufacturer has created an ethanol treatment. If it did work and had proven effective in R&D tests they would sell it.
                            DO YOU HAVE: GOOD COMPRESSION, PROPERLY TIMED SPARK, PROPER FUEL AIR MIXTURE?

                            Comment


                            • #15
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                              Re: 2003 yamaha 115 4 stroke bogs down, misses badly above idle

                              I had the exact same problem with my 2001 115hp yamaha 4 stroke that I just purchased. Apparantely was fine last fall. Start up was fine in late April then sat until last weekend and when I ran it.. started bogging, miss fire. Well my brother-in-law works for an auto supplier and got me some kleen flo injector fluid. So I dumped a bottle into the tank and run it last Thursday night...seemed to help a bit. Ran it the next day and sure enough problem gone! Not sure if it was the kleen flo or just that it only sat for a short while with the problem. Anyways...doesn't hurt to try a bottle...mine was free but I think they are around $6-8 a bottle...maybe a litre size...not sure. Good Luck! btw...love this motor...it's on a Bennington 2575 FS Pontoon.

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