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Won't Idle - Here's what I did to fix it!

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  • Won't Idle - Here's what I did to fix it!

    My 9.9 2-stroke wouldn't idle. It ran well at speed, but died when I tried to idle. Discussions seemed to indicate a carburetor rebuild. Ughh...

    Fixed in 10 minutes!
    But I fixed it myself with almost no effort (after a lot of reading, of course). No carburetor rebuild, no gasket replacement, no big engine parts had to come off. I didn't have to buy anything. Of course this won't fix idle problems in all cases, but it's worth the ten munites to try doin' this first.

    I gotta confess, I now know I had water and junk in the gas can this spring, and I started up the motor before checking or cleaning the can. Problem! So I got out the manual and got online and started to read. I read about rebuilding the carb. I read about cleaning the low-speed jets in the carb - requires a teardown. But for me it's a big deal to rebuild the carb, or even just take it apart. I couldn't find much discussion on simply cleaning parts of the carburetor, although some people did mention it.

    So I read the manual more deeply, then looked on this forum, and re-read the manual, etc.

    In the end, all I did was...
    1) clean the fuel filter
    2) clean the pilot screw. Done!

    Both the fuel filter and the pilot screw are easily accessible on the outside of the engine without taking anything off but the engine cover. If you don't know where they are on your motor, look in the manual under Fuel System and locate the parts by name on a diagram.

    1) Fuel Filter - I cleaned the fuel filter by unscrewing it and blowing out the bits of dirt in the container and on the filter.

    2) Pilot Screw - Then I removed the pilot screw, cleaned it off, sprayed carb cleaner into the hole and replaced it. This seems to have been the most significant part of the fix.

    If you already know where all these things are on your outboard, this fix only takes 10 minutes.

    The fuel filter (on my 9.9/15hp 2-stroke) is on the port side of the motor and has a clear container and a nut on top. Loosen and remove the nut, pull the filter unit away from the engine a few inches leaving the hoses all attached, and unscrew the container with the filter inside. Empty it out, spray out the inside with carb cleaner or compressed air. Pull the filter screen off and be sure it is clean, too. Put it all back together.

    The pilot screw is on the upper part of the carb on the starboard side and has a spring on it to keep it place. Important! - Don't loosen this screw first! First you gotta screw it in and count the turns until it just stops (don't tighten it hard - it's a needle valve). Count the turns so you know how to put this screw back in the exact same position after you clean it. There's a table in the manual called Carburetor Set-Up Specifications and it says for my engine to back the screw off 1-1/4 to 1-3/4 turns. But when I counted the turns it was set to 2-1/8 turns - so I set it back up at 2-1/8 turns - whatever...
    So anyway, after counting the turns, unscrew and remove the pilot screw, clean it, spray carb cleaner into the hole and replace screw. Turn it all the way in until it just stops, then back it off the number of turns you counted before you removed it.

    And that's all I did. No rebuild, no carburetor removal, no gasket replacement. Nothing complicated. Nothing to buy. Just clean the filter and clean the pilot screw. 10 minutes!

    Started right up. Idled just fine. I'm back on the water.

    One note of caution! You might be tempted to do this with your motor on the boat and your boat in the water. If you drop any of these tiny parts, you're outa luck until you can get new ones. The 10 minutes I mentioned no longer applies.

    Thanks to all who contributed bits of understanding on this forum.

  • #2
    Worked for us

    Your symptoms were exactly the same as ours and we (well, my husband did it -- I do the online info finding!) did exactly your procedure plus filled the tank with fresh gas/oil.

    Seems to have worked -- let it run at idle for about 5 minutes and it didn't stall, whereas before it would stall immediately.

    Just one note -- after you do this, expect it to take quite a number of pulls to start as you have to work gas back through the system. I'm guessing it took maybe 30, whereas it had always started on the first pull. After that first start, though, it's now back to starting on the first pull.



    • #3
      I tried this also, and it worked!

      I have a 1993 Yamaha 15 hp 2 stroke which had the same issue, stalling at low idle. I have been problem solving for a week. I came across your post. I had already cleaned the fuel filter, and had been playing with the pilot screw thinking it was to lean.

      End of story, I just read your post, went down to the boat, took out the screw, cleaned it, sprayed carb cleaner into the port.

      Now it is running smooth like it has in the past.

      Thank you.



      • #4
        Does the pilot screw have another name?

        Hi, I want to try this on my F4MSHD (4hp fourstroke) that won't idle (stalls) but can't figure out which part the "pilot screw" is on my tiny little carb.

        Would it also be known as "screw, air adjusting"?

        Part #16 on this diagram: ?

        Yamaha OEM Parts ? Outboards, Outboard Motors

        Last edited by Lifeflow; 05-26-2013, 10:21 AM. Reason: Fixed parts diagram link


        • #5
          Just before I start...

          Hey there,
          I have a Yamaha 3 hp 2 stroke with a similar problem (The engine dies on low idle) I was wondering if this procedure could also work for me . I know the parts and positions may not be the same but just the general procedure is what I am looking at.

          Thanks for your time.


          • #6
            Seems to me what you actually did was alter the air mixture to allow it to idle, if unscrewing something and spraying it with cleaner was all that is required to clean the idle jet, then anyone could fix a motor with a screw driver and a spray can, my guess is nothing was blocked at all, just out of adjustment!


            • #7
              And just to add, there should be a drain bolt on the bottom of the float bowl. If you remove it, you'll drain most of the water/crap/grit from there. Recommended so you don't suck crap into a jet causing a definite carb dismantle.

              Priming the bulb with the drain bolt out will also insure any water in the lines are now flushed out as well (and your NOT re-introducing it into the carb)..

              Any carb I pull apart, or just drain, I catch what comes in a super clean small can (I use a tuna fish can) just so I can see what's in the carb. Smelling it can also let you know if the fuel is very stale and possibly varnished up the carb.
              1997 Angler 204 CC, 2006 F150 TXR