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2004 F115 Idle Issue

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  • 2004 F115 Idle Issue

    Bought this outboard with 302hrs (has 320 now just bought it this spring). Motor ran perfectly fine when I got it, once had it stall just coming back into neutral second trip out. After that point every time the engine got hot and was shut off I could not re start it without using the high idle lever. At best the engine would sputter at 500-600 rpm when the problem was occurring and when not would idle perfectly at 7-800 rpm. Problem only exists at low idle/right before neutral position in exiting gear.

    Problem has progressed to the point I can no longer even start the motor without using the high idle and it won't stay running in normal idle position to allow me to shift into gear. Once it's in gear (if I get it there) it runs flawlessly to about 6000rpm (40mph in 1750 sportfish). Problem only exists idling in neutral or starting or coming back to neutral from gear once it reaches about 1200 rpm it starts again. My IAC would rattle when I first got the engine as soon as the problem happened I did light reading and changed what I wanted to preventatively. I changed all fuel filters (cup filter, vst screen before pump, in line filter), fuel water separator, all oils, thermostat, have 4 new injectors that I installed then removed because they worked the same.

    Now at this point my iac will rattle at the beginning but by the time the engine has run 5min when I shut it off it won't rattle any longer. I am assuming it is the iac but I have done a lot of reading about this motor and realize it could be a few things. Ecu? Iac? Wire harnesses for the iac? I am going to bring it in to a local mechanic but they can't get me in for a couple weeks and I go to a lodge this week. I can get any parts I need in 3 days before I leave but wanted to try to consult the forums about this.

    With the IAC not rattling I assume it's shot. But I know it could be a wiring issue also I am worried my ecu could be damaged if the iac failed and it kept running. If I only have the issue at idle is it safe to assume it didn't fry the ecu yet or can it damage it in an isolated way? Thanks for the help regardless if I get it fixed quick I'll keep this post updated because the forums have been tremendously helpful. Thanks.

    -Patrick

  • #2
    are you saying it rattles at shut down when cold, but not when warmed up?
    and this can be repeated over and over?

    some have said they can be cleaned, but you cannot soak the whole thing.
    replacing is a good idea before it hurts the ECU

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    • #3
      I noticed while troubleshooting the problem that it won't rattle all the time. Had it happen originally when hot starting only, occuring along with the bad idle issue. Now it happens cold aswell before even being warmed up. Sometimes it will make the sound sometimes not. Mostly it won't now but it's not 100% repeatable sometimes it will even fire up no problem and make the rattle when killed.

      Is there a way to test the harness with multimeter to know its getting proper signal from ecu? Then if it is I can replace IAC knowing it is getting proper input? I should have made my post more concise. Thanks.

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      • #4
        First thing I would do is go on Yamaha publishing and download the PDF manual for your engine, if you have not already done so. Also search this forum for previous posts about this problem...especially older ones with Rodbolts replies.
        Hopefully Boscoe or Fairdeal will see this post and help you out..as they are in the know about these things!
        First thing they will want to know is the exact model of your engine..

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        • #5
          I will do all of that tonight and I will try to get a video uploaded to link to.

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          • #6
            I have almost same issue for my F50 outboard four strokes. On a lake I started up engine put in idle for warming up to a fishing trip, no issue. After my fishing trip back to load my boat to a trailer, when I put it on idle, it shut off. I have to restarted up again and again to get engine going to my trailer. I am expecting to find some answers from this thread. thanks

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            • #7
              Well, the issue was resolved. Turns out according to the yamaha mechanic that the motor's idle adjustment screw must have been manually lowered probably by someone that thought they could get it to ***** slower. He re adjusted it slightly ran it on the YDS and it essentially reset the tps and all is good. Ran it 100hrs without any issue.

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              • #8
                Also to add, apparently when running at too low of an idle, the system did not have the current to properly operate the iac. Using YDS they tested the iac and it worked every time no problem and even now I have never heard it not rattle once after adjusting idle screw. This is why it would intermittently rattle on shutoff before when it was sputtering to stay running.

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