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upgrade T9.9LPB to 15hp carburetor

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  • upgrade T9.9LPB to 15hp carburetor

    I have a 2013 T9.9LPB (Primary ID 6AVAL 1021249). I am interested in upgrading to a 15hp carburetor. Based on some searches it appears there is a 15hp carb that is identical except for larger throttle diameters. My primary reason is because the low speed / idle valve seems to plug really easily and the 15hp would be less susceptible. Any feedback on this? Anyone know which the half dozen carbs for the 15hp 2013 motor is the match to mine? Thanks!

  • #2
    The difference in jet sizes between a 9.9 and a 15 HP is minimal.


    Keeping fresh fuel, preferably ETHANOL FREE, or stabilized with Yamaha's Ring Free will keep those jets clean..

    Old ethanol fuel left for over a month will about guarantee clogged jets, 9.9 or 15 HP.


    * If storing for awhile, draining the float bowl would be strongly encouraged...


    Here's a varnished up carb to a 6.75 HP engine(smaller jets yet):
    Last edited by TownsendsFJR1300; 06-11-2019, 07:51 PM.
    Scott
    1997 Angler 204, Center Console powered by a 2006 Yamaha F150TXR

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    • #3
      Thanks for the response. I have used yamalube ring free and premium gas. Not sure how I can ethanol free in CA. I had a boat repair facility recommend avgas to get away from the ethanol. I have a 9.9hp carb on order. The same facility said rebuild the 9.9 only works about half the time so I am putting out the $300 for a new one. 9.9hp carb is on back order so I am thinking about the 15hp instead - same price.

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      • #4
        Originally posted by MikeK662 View Post
        Thanks for the response. I have used yamalube ring free and premium gas. Not sure how I can ethanol free in CA. I had a boat repair facility recommend avgas to get away from the ethanol. I have a 9.9hp carb on order. The same facility said rebuild the 9.9 only works about half the time so I am putting out the $300 for a new one. 9.9hp carb is on back order so I am thinking about the 15hp instead - same price.
        Most marina's carry non-ethanol (at least down here).


        I do carb cleaning ALL the time on mowers, weed eaters, chain saws, etc. Can't comment on AV gas...

        It's extremely rare I have to replace anything (maybe a float bowl seal). The main thing is removing the main jet and the nozzle usually found under it. There are often sideways holes in the nozzle that needs to be spotless.

        As a side note, IME, I've found "Gas Shok" stabilizer to work extremely well (up to a year), with ethanol. I learned about this product with my old carbed Evinrude 150 which kept clogging the carb (literally a week later). After using GS, I NEVER had to clean the carbs again. IME, keep away from "Stabil". I've had hands on experience with it NOT working-long story..

        Lastly, Investing in a small Ultra Sonic Cleaner would be a lot cheaper than a new carberator. A shop stating (IMO), a rebuild only works half the time is BS, IF it's CLEANED correctly.



        Below is a pic of fuel lines from a weed eater I repaired. The really bad part of the line was from inside the fuel tank(with fuel). The "better" line was not soaked in ethanol..






        Here's an "AFTER" pic of the same carb (previous pic) cleaned thru the Sonic Cleaner with no other assistance from me:





        Scott
        1997 Angler 204, Center Console powered by a 2006 Yamaha F150TXR

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        • #5
          Originally posted by MikeK662 View Post
          I have a 2013 T9.9LPB (Primary ID 6AVAL 1021249). I am interested in upgrading to a 15hp carburetor. Based on some searches it appears there is a 15hp carb that is identical except for larger throttle diameters. My primary reason is because the low speed / idle valve seems to plug really easily and the 15hp would be less susceptible. Any feedback on this? Anyone know which the half dozen carbs for the 15hp 2013 motor is the match to mine? Thanks!
          First you should find a new repair shop. Carbs can be cleaned over and over...with 99% success rate....if done right. Unless there is something broken off it or its corroded to hell..then it can be cleaned and rebuild.

          A 15 carb is going to plug up just as easy as a 9.9 will. The problem is how is the carb getting plugged repeatedly.

          Can you clean the carb yourself?

          I assume you are running off a portable tank? If so, do you let fuel sit for long periods of time between uses?

          Do you run the engine dry of fuel before storage and/or use fuel stabilizer?

          You could consider adding a external filter/water separator to your set up.

          Cancel the order for the carb, find someone to clean yours properly and address the issue of where the crap is coming from.

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          • #6
            Thanks for all the great advice. Frankly, this is the first board I've tried and gotten knowledgeable / helpful responses! I am pretty handy but honestly carbs and I have never gotten along. I agree the 50% didn't make much sense to me. I will add the sonic cleaner to my father's day list and try my hand at a rebuild. The tank does sit out, but I burn through the 3 gallon tank every 4-8 weeks. I will look around for non-ethanol. The first marina I called said all there gas is e-10. AVGAS has lead but it doesn't look like this small motor has a converter. Another option I will check is local race track.

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            • #7
              Just an FYI, ethanol fuel W/O being treated can go bad in as quick as one month.

              Leave some out in an open container on a humid day and you can watch the fuel turn cloudy with water/moisture.


              I'd suggest once up and running, use your fuel inside a month, put the balance in your car. (FI systems are not nearly as finicky and it'll be diluted).

              As noted earlier, if sitting for more than a month, simply drain the float bowl (one screw), and eliminate any varnish from building up..
              Scott
              1997 Angler 204, Center Console powered by a 2006 Yamaha F150TXR

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              • #8
                The greatest fear with "operating" (cleaning) on carburettors stems from the fact that they made of many little delicate components, and considerable mystery surrounding how they actually work and are put together.
                It is very difficult to work on these if your dexterity is challenged or if you are ham fisted but there are things that make this task easier.
                Take plenty of pictures before and during, use plenty of light. Use only screw drivers that are in excellent condition. Use copper or aluminium wire carefully but thoroughly into all passages. Use an ultrasonic cleaner. Soak, take your time don't force anything.
                I tended to rush to complete this task in a short time, in the past, because I was fighting against memory loss: to get it done before I forgot how it all went together. I can now relax, take the time because I can now take copious amounts of quality pictures with my iPhone or iPad and have the facility to zoom in on them.

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