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2017 DF140A Overheats at 6000 rpm.

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  • 2017 DF140A Overheats at 6000 rpm.

    I pulled the diagnostics on it and it has done the 1400+ times. I am the second owner and have been boating all my life. All electrical connections are tight, Water flow appears to be fine from the tell tale and gauge. But the gauge drops to zero at times, I assume it works like the thermostat and opens/closes as needed but i am not sure.. I have replaced the impeller and all water flow tubing, Spark plugs and all other maintenance on schedule with the manual. I have to stay at 5800 or less at all times or it will overheat. Sometimes it does it at lower rpms but it seems to be a false alarm because the beep goes away and the motor starts and runs fine afterward. When it overheats at 6000 rpm i have to wait for it to cool down for about 10 minutes. Any ideas would be greatly appreciated.


  • #2
    Did you install a full water pump kit, or just the impeller? You need to do the FULL kit because the stainless housing may get a slight deformation thats not easily visible to the naked eye and this will affect the pump’s performance particularly at high revs.

    Regarding the alarms there are 2 temp alarms, one is temp absolute (engine reaches the factory set “too hot” limit) and temp gradient (engine temp changes too rapidly) so you could be getting either of them in different circumstances. They will show separately in the ecu history on the SDS software.
    Last edited by Moonlighter; 06-12-2022, 09:57 PM.


    • #3
      Also what boat is this engine on? Are you sure that the engine isnt set too high?


      • #4
        I did replace the full impeller kit minus the top housing. The motor is on a 21ft Shallow Sport Flats Boat. The top housing has the stainless steel housing inside of it and i did replace that along with all gaskets including the rubber ones. Another question is when i am flushing it on the muffs there are a couple of holes that leak water out on the lower unit is that normal? Thank you guys for the help.


        • #5
          I am suspicious that your engine may be mounted too high resulting in it not being able to draw water into the water pump at high speed when the hull is lifted high out of the water.

          Holes on lower unit with water coming out is normal.

          can you post photos that show the engine height particularly the anti vent plate in relation to the bottom of the hull?

          its not hard to change the height with a 140, they arent too heavy to move up or down using the boat trailer method - see the sticky thread re engine height and propellor selection, it is explained there.


          • #6
            Do these have a poppet valve?


            • #7
              Yes it does have a poppett valve. It is also mounted on a Hydraulic jack plate. I am also not familiar with what exactly the poppet does other than regulate the water flow. It seem's to me that would be the thermostat's job.


              • #8
                I have always been told that overheating at high rpms but not lower speeds or idling is a symptom of bad poppett valve.
                I believe, as you go faster, more water is pulled up into the powerhead, more than is being expelled through the water passages
                this is when the water pressure pushes the poppet valve open and it "dumps" the excess water coming into the head.
                I have also seen poppet valves have trash clogging them, easy to pull and check.
                Others, more knowledgeable can chime in
                Last edited by ECU1984; 06-15-2022, 11:16 PM.


                • #9
                  ”If cylinder water pressure is high with the thermostat closed the water pressure valve will open to relieve the pressure.” Quote from my 2009 DF90A service manual. The service manual doesn’t specify where the excess water is sent. My water pressure valve is located on the mid unit so I would ASSUME the excess water is dumped into the drive shaft housing then out through propeller exhaust. This appears to be in contradiction to ECU1984 post #8. Please note I’m ASSUMING.


                  • #10
                    I probably had it backwards, bad poppet valve is overheating at low rpms but not overheating at higher rpms.