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'09 15hp 4 stroke wont run without choke and I need to push prime and goose it a lot

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  • '09 15hp 4 stroke wont run without choke and I need to push prime and goose it a lot

    Hello. I just bought a 2009 15hp Mercury 4 stroke and it ran rough on the test drive. (11.5' dinghy) It wouldn't idle with the choke in, but started on the 3rd pull. I took it out, about 5 minutes no wake speed, then WOT for another 5+ minutes. It planed fine and went pretty fast. I could push the choke in if I was over 1/2 throttle. I got the price down another $300 and told him I'd deal with it. He seemed to think that it was caused from storing the engine for 3 days on the side that it says not to store it on. Some oil leaked out. I changed the oil and took a look a the spark plugs. they were dark tipped and black on the end of the threaded part. I bought new ones, but they were the wrong type so I cleaned the old ones. It had the same symptoms, on the way out (choke out). I nailed the gas and it started to bog bad, so I put the choke in and it took off with no issues, going faster than on the test drive. I thought it was cured, but then it got much worse. It wouldn't run at all with the choke in, at any throttle, and with the choke out, it would no longer plane. The bulb on the fuel line was still hard, and pumping it did nothing, but when I would goose it to hit the accelerator pump, it would rev up. It would also rev up and run way better if I pumped the prime bulb continuously. I pulled the fuel filter and I could blow through it easily. The engine probably has 20 hours tops.

    I'm wondering if there is any type of foam air filter in that plastic piece on the carb. I reached around and I could feel a plastic piece with holes in it, but it looks like I pain to remove so if there is no foam material in there it would be a waste. I'm not sure that a clogged air filter would ever cause it to run lean, only rich. I'm thinking it might be the fuel pump, or the carb, but some input from you guys might help me save time troubleshooting this. Thanks in advance!


  • #2
    Re: '09 15hp 4 stroke wont run without choke and I need to push prime and goose it a

    No air filters on 2 strokes. Don't know about 4 strokes.....probably not. They have an air induction system (plastic shroud over carb air inlet) on 2 strokes to reduce noise. Don't know but suspect 4's have that too but could still be without air filter.

    Fuel filters yes. Bad fuel a possibility. Crudded up carburetor (replacement kit) fuel pump......in that order. Adding some Sea Foam to the gas tank (with fresh fuel) can help to clean up minor problems like you are having and may keep you from moving into the carb kit requirement.

    Mark
    If you are new to boating or have a new boat, a knowledgeable friend could show you how to operate your boat and save you a lot of grief, maybe some money, and maybe your life.

    Comment



    • #3
      Re: '09 15hp 4 stroke wont run without choke and I need to push prime and goose it a

      Thanks mark! I took it for a couple rides today. All of a sudden it would run normal. I did wot for maybe 3 min, then it would shut down and bog hard. I would have to goose it or pump the prime to keep it running, with the choke on too. I got it to idle for 15min with the choke in too. I pulled the line on the fuel pump, ad gas comes out. When its acting up, it won't hold a high idle in neutral. It seems like there might be crud in the carb. Carb rebuild time? Does anybody know what carb the 20hp takes because I heard that that is the only difference between the 15 and 20. I know they are the same displacement nd same weight. (Phone post)

      Comment



      • #4
        Re: '09 15hp 4 stroke wont run without choke and I need to push prime and goose it a

        Hey...I have the same problem with an '08 15hp Mercury 4 stroke. Did you ever get this fixed?

        Thanks!
        Joey

        Comment



        • #5
          Re: '09 15hp 4 stroke wont run without choke and I need to push prime and goose it a

          Had the same problem on a used 18 rude I bought from a farmer who had it in his barn for "awhile". After experiencing what you are, and before I knew of Sea Foam which will clean out minor crud, I pulled the carb and yes, it contained significant varnish and cleaning and adding a new kit fixed my problems.

          Mark
          If you are new to boating or have a new boat, a knowledgeable friend could show you how to operate your boat and save you a lot of grief, maybe some money, and maybe your life.

          Comment



          • #6
            Re: '09 15hp 4 stroke wont run without choke and I need to push prime and goose it a

            I havent worked on mine yet, but I did find out that you can replace the jets and turn the 15 into a 20hp. I'll do that when I take the carb out.

            Comment



            • #7
              Re: '09 15hp 4 stroke wont run without choke and I need to push prime and goose it a

              Originally posted by jgorm View Post
              I havent worked on mine yet, but I did find out that you can replace the jets and turn the 15 into a 20hp. I'll do that when I take the carb out.
              That sounds really interesting. Do you have a link to a website that shows how to do that?

              Thanks!
              Joey

              Comment



              • #8
                Re: '09 15hp 4 stroke wont run without choke and I need to push prime and goose it a

                Originally posted by Texasmark View Post
                Had the same problem on a used 18 rude I bought from a farmer who had it in his barn for "awhile". After experiencing what you are, and before I knew of Sea Foam which will clean out minor crud, I pulled the carb and yes, it contained significant varnish and cleaning and adding a new kit fixed my problems.
                Mark
                I'm thinking dirty carb is the problem here as well. Everything else looks good. I did notice that my bulb on the gas tank doesn't "always" pump up tight. Fells like it is pushing gas back into the tank. Maybe I should replace the tank and line to be safe?

                Joey

                Comment



                • #9
                  Re: '09 15hp 4 stroke wont run without choke and I need to push prime and goose it a

                  Originally posted by jorjo View Post
                  That sounds really interesting. Do you have a link to a website that shows how to do that?

                  Thanks!
                  Joey
                  No. I posted this on another forum. I've heard of people doing it, but its all second hand info and I never found any posts online of people that actually did it. I'll do it, but it will be a couple months before I get to this project.
                  I just got the part list, and guess what, its the same for the 15 and 20. Here are the only differences between the 2. They have the hp rating in bold when they are different and I went through the entire parts list. The heads, crank, and camshaft are the exact same.
                  Code:
                  PN: 3303-853720T14 carb assembly 15 hp tiller
                  PN: 3303-853720T15 carb assembly 15 hp remote
                  PN: 3303-853720T16 carb assembly 20 hp tiller
                  PN: 3303-853720T17 carb assembly 20 hp remote
                  * I'm not sure if these part numbers include everything in the carb.
                  
                  PN: 803689008 15 HP JET, pilot (#46)
                  PN: 803689009 20 HP JET, Pilot (#52)
                  
                  PN: 19-802702002 15 hp plug
                  PN: 19-802702001 20 hp plug
                  
                  PN: 812650021 Main Nozzle 15hp tiller
                  PN: 812650019 Main Nozzle 15hp remote
                  PN: 812650022 Main Nozzle 20hp tiller
                  PN: 812650020 Main Nozzle 20hp remote
                  
                  PN: 802701011 Jet Main #121 20hp
                  PN: 802701010 Jet Main #99 15hp
                  * It looks like you may need the carburetor assembly for the 20hp to fit the above parts into, but I can't tell from the drawings.  It might just be an either or type of thing
                  
                  PN: 48-897750A10 15hp propeller (9.25" x 9 pitch)
                  PN: 48-897752A10 20hp propeller (9.25 x 10 pitch)
                  This is for a 2009 4 stroke model, but there are a bunch of serial numbers listed. I think my plan will be to buy the prop, nozzle, plug, and jets and see if they fit in the same carb body. Fingers crossed! (I probably won't get to this project for a while due to my long project list, but its gonna happen!)

                  Comment



                  • #10
                    Re: '09 15hp 4 stroke wont run without choke and I need to push prime and goose it a

                    Originally posted by jgorm View Post
                    No. I posted this on another forum. I've heard of people doing it, but its all second hand info and I never found any posts online of people that actually did it. I'll do it, but it will be a couple months before I get to this project.
                    I just got the part list, and guess what, its the same for the 15 and 20. Here are the only differences between the 2. They have the hp rating in bold when they are different and I went through the entire parts list. The heads, crank, and camshaft are the exact same.
                    Code:
                    PN: 3303-853720T14 carb assembly 15 hp tiller
                    PN: 3303-853720T15 carb assembly 15 hp remote
                    PN: 3303-853720T16 carb assembly 20 hp tiller
                    PN: 3303-853720T17 carb assembly 20 hp remote
                    * I'm not sure if these part numbers include everything in the carb.
                    
                    PN: 803689008 15 HP JET, pilot (#46)
                    PN: 803689009 20 HP JET, Pilot (#52)
                    
                    PN: 19-802702002 15 hp plug
                    PN: 19-802702001 20 hp plug
                    
                    PN: 812650021 Main Nozzle 15hp tiller
                    PN: 812650019 Main Nozzle 15hp remote
                    PN: 812650022 Main Nozzle 20hp tiller
                    PN: 812650020 Main Nozzle 20hp remote
                    
                    PN: 802701011 Jet Main #121 20hp
                    PN: 802701010 Jet Main #99 15hp
                    * It looks like you may need the carburetor assembly for the 20hp to fit the above parts into, but I can't tell from the drawings.  It might just be an either or type of thing
                    
                    PN: 48-897750A10 15hp propeller (9.25" x 9 pitch)
                    PN: 48-897752A10 20hp propeller (9.25 x 10 pitch)
                    This is for a 2009 4 stroke model, but there are a bunch of serial numbers listed. I think my plan will be to buy the prop, nozzle, plug, and jets and see if they fit in the same carb body. Fingers crossed! (I probably won't get to this project for a while due to my long project list, but its gonna happen!)
                    Since you have access to part numbers, you might check other parts like intake manifold, reed valves, and other things that COULD be different in addition to the carb jets, maybe ignition timing too. I do know that on several engines that I have followed conversations about them, there were other changes.

                    Mark
                    If you are new to boating or have a new boat, a knowledgeable friend could show you how to operate your boat and save you a lot of grief, maybe some money, and maybe your life.

                    Comment



                    • #11
                      Re: '09 15hp 4 stroke wont run without choke and I need to push prime and goose it a

                      If the bulb won't stay hard that may be part of the problem with poor running. If the diaphragm inside the bulb is bad you might not be getting proper gas flow through the bulb. Not a hard fix and a good start before re-building the carbs.
                      The dictionary is the only place that success comes before work.

                      Comment



                      • #12
                        Re: '09 15hp 4 stroke wont run without choke and I need to push prime and goose it a

                        The carb is dirty inside and needs to be cleaned properly. You will also have to drill a small hole and remove the pressed in plug that covers the idle mixture screw to properly clean that passage.

                        Notice the difference in the carb part #'s between the 15 and 20, the suffix, they are NOT the same carb. If you had both in your hands and measured the internal diameter at the venturi you would then see the difference. Changing jets would only change the fuel flow and cause your carb to run too rich. Some small motors limited power by using a restrictor spacer between the carb and intake manifold. If yours has such a spacer, remove it.

                        If the parts manual shows a break down of the carb, look at the actual butterfly (throttle plate) and see if it shows a different # for the 15 and 20 carbs. If so, changing this plate without the machine work to properly size the throat, and the corresponding taper before and after the venturi, would be useless. You would end up ruining a perfectly fine carb and end up ordering a complete replacement.
                        Last edited by CharlieB; December 2nd, 2011, 07:41 PM. Reason: additional statement

                        Comment



                        • #13
                          Re: '09 15hp 4 stroke wont run without choke and I need to push prime and goose it a

                          The manual is the same for both the 15 and 20 hp versions. I have both the OEM service manual, and the parts manual. It clearly shows when there is a different part between the 20 and 15 hp versions. I checked every single part and those mentioned are the only parts that differ. everything else is identical.

                          Comment



                          • #14
                            Re: '09 15hp 4 stroke wont run without choke and I need to push prime and goose it a

                            I have a 2010 Mercury 15 and I think that the cam is different on the 20. I find it REALLY hard to believe that different jets can give you 5 more horses.

                            Interesting.

                            Tronald G. Esterhaus

                            Comment



                            • #15
                              Sign up today
                              Re: '09 15hp 4 stroke wont run without choke and I need to push prime and goose it a

                              They make the 15 for those dinghys that have a 15hp max hull rating. The cam is the same, the bore and stroke are the same, the head is the same, etc. Buy the parts guide and see for yourself.

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