Yamaha 150 flushing concerns

Discussion in 'Boats, Motors, Trailers and Towing Rigs Forum' started by MikePA, May 31, 2020.

  1. MikePA

    MikePA Member


    I went and looked at a 2017 Yamaha 150 last week and asked to see it running. To my surprise the owner hooked the hose up to the flush port at the side of the Cowling instead of using the typical flushing ports and muffs at the bottom of the leg.. not being familiar with this engine I asked if you can use that port while the engine is running and he assured me you could... Will this not mess up the impeller?!
    Last edited: May 31, 2020
  2. prodjsaig

    prodjsaig Active Member

    Some people don't know how to treat a motor. I went and looked at a 06 150 Yamaha 4 stroke when I got there the two guys said they used muffs and no water was coming out and thought they messed up the motor. Did this without telling me or listing it on the ad.

    Anyway sure enough the service center said bad thermostat... so not only they didn't run the engine and flush properly they didn't perform any or much required maintenance. You need a good set of muffs or a garbage can with water.

    But the flush port is ok to flush just don't run the motor.
  3. profisher

    profisher Well-Known Member

    Running the water pump dry for to long can damage the rubber impeller. The worst case scenario is if the impeller comes apart and chunks get lodged inside the powerhead, blocking water passages.
  4. MikePA

    MikePA Member

    Thanks for the responses. So when he ran it, water was flowing fine through all the outlets, so assuming nothing is clogged.. if this is the case.. if I run with muffs from here on out should be good?
    Last edited: May 31, 2020
  5. Pineapple Express

    Pineapple Express Well-Known Member

    Pretty sure that Yamaha owner manuals say to NOT run the motor when the hose is connected.
  6. Pineapple Express

    Pineapple Express Well-Known Member

    If you're buying that motor I'd change the impeller ASAP for piece of mind. From there, you can flush your motor with muffs or with a hose (without running).
  7. MikePA

    MikePA Member

    Ya it definitely does say do not do that. Would the water from that port not make it to the impeller?
  8. Foxsea

    Foxsea Well-Known Member

    Even though Yamaha says no the flushing connection will get enough water to the pump AT IDLE. Do not run up Rpm's or the impeller will be damaged. I've done it at idle many times and know others that do the same. I just did a routine impeller replacement. The impeller was in perfect condition.
  9. MikePA

    MikePA Member

    Ok that is great to hear. Hopefully he didn't run at rpms haha
  10. tubber

    tubber Well-Known Member

    this is a pdf for my 2003 Mercury 4s which may have been been built by Yamaha
    This topic has come up before and seems to have conflicting opinions from knowledgeable people.
    I use a plastic 45g drum because I have one.
    Screenshot (8).png
  11. CIVANO

    CIVANO Well-Known Member

    Safest way with never any worries is a stock tank
  12. MikePA

    MikePA Member

    Interesting, thanks
  13. donnie d

    donnie d Active Member

    I would recommend against muffs also. You want to make sure your leg is underwater up to or past where the impeller housing is. Learned the hard way.
  14. MikePA

    MikePA Member

    Because even though water is coming out the appropriate outlets it still may not be sufficient?
  15. donnie d

    donnie d Active Member

    I’ve never been able to get it out the tell tale with the muffs, so I just don’t bother. I flush after each use just using the hose attachments, not running the motors.

    I live in the interior so salt water use is limited to about a month each year...ideally after a WCVI trip I’ll dunk the trailer and boat in a lake and run the motors to flush...then still flush on the hose when I get to my destination.

    mine is an F150 2018.
  16. profisher

    profisher Well-Known Member

    Everyone should invest in a water pressure gauge for your dash. I've had one on my current boat since new and it reads 15-20 psi while on plane and 5 psi while on the muffs, which is more than ample at idle. That gauge has saved my many times over the years from having the engine get hot enough to set off the alarms. Most of the time from crossing the harbour during daybreak, at low tide with eel grass clogging the inlets. I have a routine of watching that gauge closely during my harbour run and shut the engine down to an idle as soon as my water pressure begins to drop, put it in reverse and give it some throttle...which uses the prop to blow anything on the leg away. When pressure returns to normal I carry on
  17. Hagar

    Hagar Member

    I have a 2017 115 Yamaha when I flush from the top no water comes out the tell tail.
  18. profisher

    profisher Well-Known Member

    The tell tale will piss water once the t-stat opens up. If the motor is not running there is no heat to open it up.
    Oly1 likes this.

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