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Yamaha 50 4-Stroke Will Not Pee

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  • Yamaha 50 4-Stroke Will Not Pee

    First of all let me preface this all by saying that I'm not an outboard mechanic. Although I am mechanically inclined to some degree.

    Boat has been sitting for a few months. I noticed a few days ago when I started it up that it would stop peeing for a second or so and then start-up again. I didn't really think anything of it, figured that whatever was in the system had worked itself loose. However, after fixing my initial throttle linkage issue starting the engine once again... I got absolutely no water coming out of the telltale (even after poking with a paper-clip, etc).

    I hooked-up a garden hose to the flush adapter and water comes out of the telltale hole.

    So, I may have taken a bit of a diagnostic leap... but, I figured that I had a pump issue.

    Removed the lower-unit and checked the impeller but it looks brand new (no visible defects, at least).

    Any ideas?

  • #2
    Re: Yamaha 50 4-Stroke Will Not Pee

    good luck on getting a answer. My post about impeller has been sitting here for days and not one answer. I am going to take the lower unit off tomorrow and replace the impeller, I guesss that is what it is, the guy I bought it from had it over a year and never changed it, so it is due. I am not peeing either. It is either stopped up or the impeller went bad. Sounds like yours is stopped up. If it was me, while you had it apart I would run compressed air throught the passages, thats what I plan on doing. good luck.


    • #3
      Re: Yamaha 50 4-Stroke Will Not Pee

      Not the expert here but it's my understanding that the pump works from suction rather than the impeller working like a waterwheel. My point is, any scoring in the wear plate or imperfections in the rubber impeller, gaskets, orings may break the suction and it wont work right or to the extent where it will pump with enough pressure to make it all the way to the top of the engine.
      Like I said in an earlier post, you may want to run the engine for a short time with the thermostat cover off, to see what kind of circulation you are getting. If water makes it to the thermostat, then it may be a clogged telltale. Good luck


      • #4
        Re: Yamaha 50 4-Stroke Will Not Pee

        Thank you for your timely replies.

        I think I'm going to blow it all out with compressed air, put the lower unit back on and see if anything's getting to the thermostat.

        My only true worry is running it when it appears not to be circulating water. How long can I run it without damage? Or, will the alarm sound before any real damage can occur?


        • #5
          Re: Yamaha 50 4-Stroke Will Not Pee

          If there is no telltale stream after 20 seconds shut it off because after a minute or more there still won't be any water.


          • #6
            Re: Yamaha 50 4-Stroke Will Not Pee

            My Suzuki was doing the same thing.
            The impeller was also good and there wasn't any blockages. I fiddled with it for an hour or two and it started peeing again but not like the Stallion stream like before. It would pee for a while then I would turn my back and it would quit then eventually start up again.
            I was going fishing the next day so I wasn't going to let this stop me. I got on the water and everything functioned fine the entire trip and all the trips after that.

            I believe the problem was the muffs. When I did get it to pee at home it was in a bucket and I had to throttle up to get it to go.

            My advice is to put it in an lake and see if it works there.

            The best way to flush it would probably be to drop the lower unit and stick a hose with a jet nozzle into the water tube.


            • #7
              Re: Yamaha 50 4-Stroke Will Not Pee

              I guess I will hi jack your post as no one will answer my impeller question. You and I seem to be in the same place. I just got done changing my impeller, used compressed air to blow out all the passages, hooked up a water hose to the tube and it pees good, how ever it still will not pee when i start it. I ran it with muffs and in a barrow, nothing. I guess the next step is to get the whole water pump kit as i do not know what to do. Anyone have any ideals?


              • #8
                Re: Yamaha 50 4-Stroke Will Not Pee

                Cleaned everything out well, put it back together and dropped it in the water... after about 20 seconds she was peeing.

                Now I just have this issue w/ it bogging-down and not wanting to rev past 2800 rpm. But, I suppose that is for another post.

                Thank you for your help, so far, everybody.


                • #9
                  Re: Yamaha 50 4-Stroke Will Not Pee

                  Hi: I seem to have a similar problem. I have my boat is a 2007 Wellcraft 180 with 115 Yamaha. It was sitting for about two months since last launch in October. I just winterized it yesterday in 35F degree weather. I started up after the oil change with the lower unit submerged in a big rubbermaid container. No peeing. I connected the garden hose to it and got a steady stream. I read somewhere that there could be a thermostat which could prevent water from peeing if it's not warmed up. Is this true that yamaha outboards have thermostats?



                  • #10
                    Re: Yamaha 50 4-Stroke Will Not Pee

                    Yes, they should all have thermostats. If you want to test it, my shop manual says for the 115:

                    "The thermostat is located under a small cover directly on top of the cylinder head. the cover has one hose attached to it and can usually be installed in either direction, so be sure to matchmark it to the cylinder head before removal. Otherwise the cover is secured by 2 bolts and is easy to remove."

                    I highly recommend picking-up a repair manual for yourself... it really is invaluable.


                    • #11
                      Re: Yamaha 50 4-Stroke Will Not Pee

                      Thanks for the reply. I feel better now. I was worried that my water pump or impeller may have problem. I'll try again in the spring time see if it will pee in warmer weather. I'll take your advise to get a shop manual...I got all winter to read it cover to cover.


                      • #12
                        Re: Yamaha 50 4-Stroke Will Not Pee

                        Be wary of using muffs. You are running under fawcett pressure and the pump may not be working.
                        Also the pump needs to be completely submerged to have a chance of working. It is not self priming. Either get a real deep tub or put the boat in the pond.
                        If the impeller has not been replaced in the past year it could be defective. If the motor has been parked, not used, for more than a year the impeller could be set and not work correctly. If the pump plate or the housing is scored or pitted, water will bypass the impeller. If the impeller was incorrectly installed, ie the drive shaft was not rotated clockwise, looking from the top, as the housing was pressed down over the new impeller, then the impeller blades are not set correctly and will not pump fully.
                        Pay attention to the alignment and sealing of the water tube.
                        If an impeller has come apart, pieces may be blocking the tube or waterways.
                        The tell tale jets often block up so this is always the first check.
                        Thermostats don't fail too frequently but it does not hurt to test or replace.
                        Over time, salt water use can cause corosion and help block waterways and cause thermostats to stick or fail.
                        You should get a good tell tale stream at idle, warm or cold.


                        • #13
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                          Re: Yamaha 50 4-Stroke Will Not Pee

                          I just had this exact same problem with a yamaha motor. Impeller was fine, thermostat was ok, no pee stream.

                          The last thing I did was removed the brass T fitting at the bottom of the cylinder heads. You can find this by tracing the rubber pee hose back towards the block. Unplug the two rubber hoses and unscrew the brass T. This is the outlet for the water. Check the brass fitting by blowing into each end. There shouldn't be any restriction. If there is your fitting is clogged, clean it put. I found a big rubber piece of the impeller sticking out of one hole and another rubber piece wedged inside the fitting.

                          If you don't find anything blocking the fitting, start the motor with the fitting removed. Water should come out of the hole the fitting was removed from. If it doesn't, there might be something blocking the water in the block or the impeller/thermostat is bad.

                          If water is coming out of that hole and there is no debris in the T fitting your rubber hose is clogged.

                          Good luck,