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DF350 duo prop

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  • DF350 duo prop

    I am just completing the 500 hour service on a pair of 350s ..I am impressed with the design ease of the work needed done. I am seeking help on the water flow. At the end of last season the water indicator quit working..first just a dribble then entirely on the port engine ..starboard engine was slow but steady. After completing the service on both ngines and finding partial blockage on the starboard engine it now flows perfectly but the port engine has no water flow. Running in a tank it heats up to temp and stays there indicating the pump is working fine. It has no water flow either on the hose or running. The stb engine flows on both.
    I’ve traced all the hoses that I can see and they are clean..
    where can the blockage be??
    Thank you

  • #2
    Sounds like an open by-pass valve (to much water flowing through by-pass valve back to exhaust), probably needs cleaning/replacing? If running in a tank, could try running (depending on size of tank) 4 - 8 gals of vinegar (idling) for about 1.5 - 2hrs each motor recirculating same water-vinager solution. If same water gets too hot, let it cool down and run again (total time 1.5 -2 hrs). If by-pass valve starts working again, should be fine, if not you might have to replace that valve. Run fresh water through motor within a few hrs after vinegar flushing.

    Good luck, post back on what you find out.


    • #3
      Thank you..I will try that ..can’t hurt to clean the inside
      how hard is the valve to change ?


      • #4
        Looks like about a $15 part, part #6 on thermostat parts pic page.
        I don't have a 350, and couldn't tell you how accessible that part is.
        You could check with your Suzuki people near you at what it would cost to replace them, and how long? That might give you an ide?

        Good luck, post back on what you find out.


        • #5
          Goggle m a n u a l s L i b (all one word), they have a service manual for a 2017 DF 350 for download, free I believe but I didn’t read the fine print.

          I’d bet the the by-pass valve is bolted to the mid unit.(side panels removed)


          • #6
            It was easier then I made it but learned a lot along the way. I do have a manual and it does show water flow however I am not good at transfering the diagram to the hoses on the motor....I checked the presure / by pass valvue .. very clean and working.

            the problem was a double block; one in the hose between the lower unit and the block..and another just above that.. taking each air hose off and blowing through it cleared it all out..

            I did run the vinager through the motors hopefully will disolve the bits and pieces so they flow through the system

            A couple of notes to forward on to anyone that goes through this process
            although some services do not require removing all the cowling I highly recomed going through the trouble ... I found three hose clamps that are mostly rusted through.. would have never found those.. also the zincs inside needed replaced.

            looking forward to the test run in puget sound before the launch at Westport and salmon fishing.

            THANK you for taking the time to help