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Question for the pros about a 1992 Yamaha MSHQ

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  • Question for the pros about a 1992 Yamaha MSHQ

    Hello everyone. My project is coming along on my 1992 Yamaha 40 hp 3 cylinder thanks to all the help. I have a question. I’ve got a new portable fuel tank, all new fuel line from tank to carburetor with oem line under the cowling. New fuel water separator as well. Carburetors completely rebuilt with all new jets , everything. Pilot screws out 1 1/2 turn. Hard to start , rough idle and a sneeze after all this done. Tried adjusting the pilots 1/4 turn at the time but no difference in idle on any of them. Runs good at wot. Here’s my question I noticed the new connectors at the motor where leaking and bulb not getting tight. Only thing I can think of is they’re not compatible so I replaced both with the old ones. Bulb pumps up and holds prime now and no leaks. Problem is I have not had a chance to run it yet after doing this. Do any of you think this could’ve fixed my troubles? Was I getting air from the connectors while it was running? It’s driving me crazy not being able to run it yet since I found those fittings so I thought I would bug you nice people for opinions. Oh when it did idle it was kind of high at around 950rpms. I’m hoping this fixed it all after everything I’ve got in it with other repairs as well. Looking forward to hearing what y’all think. I’d really appreciate it.

  • #2
    I would not think those connections would have anything to do with the hard starting, fast idle, or the lean sneezing.

    did you follow the link and sync procedure in service manual after putting the carbs back on?
    have you checked to see if timing is in spec at idle?
    did you go thru the prime start system , making sure all the passages are clear, heater works, diaphragm and check valves all are in good shape?
    is the red lever on the prime start in the auto/normal position?
    did you try turning it to the open position to see if that helped to get it started and then turned to off or the auto position to run once started?

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    • #3
      Clean the carbs properly, fix the fuel leak and test again.

      Comment


      • #4
        I’m finally going to be able to move the boat back to the driveway where my water source is so I can see how it runs. If still the same problems I’ll go back to the manual for the link and sync again. It just has a manual choke and there all closing all the way and opening all the way. Leak is fixed and the carburetors where spotless with all new jets, everything. I must have cleaned the carburetor bodies 10 after soaking just because I didn’t want any dust that may have accumulated while waiting on parts. Unless something got in the system anyway. Anything’s possible. Timing should be good since it was actually running smooth until the carburetors started leaking which is why I opened them up and then found the mess. Lol I’ll let y’all know what happens. Thanks so much for the input. It’s greatly appreciated.

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        • #5
          Yamaha carbs are very hard to clean, they are easy to make look nice, but cleaning requires a lot more than washing, soaking, spraying and looking at.

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          • #6
            Originally posted by Douglasdzaster View Post
            I’m finally going to be able to move the boat back to the driveway where my water source is so I can see how it runs. If still the same problems I’ll go back to the manual for the link and sync again. It just has a manual choke and there all closing all the way and opening all the way. Leak is fixed and the carburetors where spotless with all new jets, everything. I must have cleaned the carburetor bodies 10 after soaking just because I didn’t want any dust that may have accumulated while waiting on parts. Unless something got in the system anyway. Anything’s possible. Timing should be good since it was actually running smooth until the carburetors started leaking which is why I opened them up and then found the mess. Lol I’ll let y’all know what happens. Thanks so much for the input. It’s greatly appreciated.

            maybe you have the wrong carbs on the motor if you say it has chokes

            this shows it has a solenoid valve but it does not look like it has any linkage that attaches to it to close choke plates on the carbs
            Yamaha Outboard Parts by Year 1992 OEM Parts Diagram for CARBURETOR | Boats.net
            Last edited by 99yam40; 3 days ago.

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            • #7
              Originally posted by ausnoelm View Post
              Yamaha carbs are very hard to clean, they are easy to make look nice, but cleaning requires a lot more than washing, soaking, spraying and looking at.
              I’ve been a small engine mechanic for years and done hundreds of carburetor jobs. These were my first outboard carburetors to tackle but every passage way is clear on the body and all of the parts are new. I replaced everything. I use a magnifying glass to inspect everything which is why I cleaned them multiple times. Being my first outboard I’m not saying i couldn’t have missed something but I was very thorough.

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              • #8
                Originally posted by 99yam40 View Post


                maybe you have the wrong carbs on the motor if you say it has chokes

                this shows it has a solenoid valve but it does not look like it has any linkage that attaches to it to close choke plates on the carbs
                Yamaha Outboard Parts by Year 1992 OEM Parts Diagram for CARBURETOR | Boats.net
                I’ve seen that diagram and was wondering about that. I got this for a project and I’ve found and fixed some messed up stuff that was just rigged instead of repaired. And very neglected maintenance wise. I finally got my hands on the correct service manual and it shows the carburetors that I have with the choke. Yamaha made I don’t know how many different models and they’re all close. It was running great. I was very happy. Then the carburetors started leaking. When I saw the inside of the carburetors I don’t know how it was running so good or at all for that matter. All I could say was go Yamaha! Lol When I get to run it (hopefully in a day or so) if it’s hard to start or anything I’m going to start over with the link and sync procedure . If that doesn’t work I’ll pull the carburetors again and get my magnifying glass back out. Thanks for going to the trouble of finding that diagram. I appreciate it.

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                • #9
                  Originally posted by ausnoelm View Post
                  Yamaha carbs are very hard to clean, they are easy to make look nice, but cleaning requires a lot more than washing, soaking, spraying and looking at.
                  I’ll be able to bring the boat back tomorrow and start it. If I end up pulling the carburetors again what should I do differently? I soaked them then I used a set of brushes I have for carburetors (they’re kind of like pipe cleaners). While spraying them after which I used compressed air. Just the bodies because I replaced everything else. This is my first outboard and I’m stumped at what to do different. At first it ran great after reinstalling. The third trip out is when I started having difficulty. I felt pretty good about them being cleaned. I may have not done the link and sync correctly. Didn’t have the manual. Now I do and was going to do that and if no change pull the carburetors and take them back to the table.

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                  • #10
                    well, does this thing have the solenoid valve on the bottom carb?
                    what does it hook onto and what does it do when operated?

                    I have read a heated sonic bath cleaning is sometimes needed to get all passages cleaned properly.

                    I have heard in the past these multi carb motors are like several single cylinder motors tied together.
                    If you do not sync them properly they will fight each other
                    Last edited by 99yam40; 1 day ago.

                    Comment


                    • #11
                      Originally posted by 99yam40 View Post
                      well, does this thing have the solenoid valve on the bottom carb?
                      what does it hook onto and what does it do when operated?

                      I have read a heated sonic bath cleaning is sometimes needed to get all passages cleaned properly.

                      I have heard in the past these multi carb motors are like several single cylinder motors tied together.
                      If you do not sync them properly they will fight each other
                      The one thing I don’t have is a sonic bath. I was afraid I would be told that. No solenoid. I’m hoping doing the link and sync will bring them together then. I hate pulling the carburetors again because the way the fuel lines are. The OEM from Yamaha seals tight which is good but they’re not very tuff it’s hard not to damage and They’re pre shaped so I don’t have a lot to cut off and make a new end. I tend to worry to much I’ve been told. If a line goes back on a little loose I can’t stand it. Gotta have a new one when with the clamp it was fine. It’s gotta be perfect. I’ve put a lot into it. It all starts with the water pump doesn’t it? Lol I noticed the admiral raising an eyebrow when she sees a new box being delivered. Lol Thanks for the reply. It’s appreciated. If there was a different way to clean the carbs I wanted to know about it. I actually know someone with a sonic cleaner. I may take them to him.

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                      • #12
                        If your guy isn't available with a sonic cleaner, a new one (decent unit) can be had for $125-$150.00 (About the equivalent of an hour labor at a Yamaha dealer).


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

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