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F225 Oveheat Problem - at Idle

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  • F225 Oveheat Problem - at Idle

    Greetings -
    Frustrating problem with overheating on a 2004 F225. Motor has 2,000 hours on it -

    At idle speeds, very low water flow coming from weep hole, and motor overheat alarm will sound after about 30 seconds of idle. At higher speeds and on plane, will run fine all day long.

    Actions so far:
    Acid flushed the inside of the motor twice to remove any deposits.
    Replaced water pump impellor (old one was still good).
    Checked thermostats per the service manual and both operate fine.
    Checked PRV valve and appears fine.

    Have lots of water flow coming from the pump - ran the motor briefly without the PRV valve in place and had lots of flow. Removed one of the internal zincs between the spark plugs and had very little flow coming out of there. I'm suspecting a clogged water passage somewhere - but hoping there is an easier approach to checking all the passages without trying to tear down the heads first. Any suggestions?

    Does anyone know the exact water flow sequence in the motor? I'm hoping to disconnect hoses at various points and try to isolate where the blockage might be.



  • #2
    2000 hrs and you wont CHANGE out the prv and stat??? youre only cheating yourself.


    • #3
      Update on problem

      Took advice from previous reply - have now changed out the water pump kit, changed both thermostats, and changed the PRV valve. Exact same problem still in place. It seems as if at idle speeds, the pump is simply not getting enough water up into the heads. With the thermostats completely out - at idle - no water comes out the thermostat holes. At 1100 RPM and above, water comes gushing out of the holes.

      I removed the plugs for hooking up the water pressure guages, and some flow of water comes out of those holes at idle, but just not enough pressure to move the water all the way up into the heads and cool the motor.

      Any more suggestions on where to look next?




      • #4
        I’m new to this site but, bringing up an old thread.

        Was this problem resolved? I have a 2003 F225 with almost the exact same issue and I can’t figure it out.

        Thermostats are functioning, poppet is functioning, tell tale is peeing, on YDS temp never gets above 180 but thermoswitch turns “on” and alarm triggers.

        Any thoughts?


        • #5
          Given the model & year of the motor,
          the symptoms are classic for the notorious exhaust rot:
          a hole eaten through the exhaust passage allows cooling water to escape -
          acting as an additional always-open poppet.

          Its easy to check for leakage,
          with the LU off and the motor tilted up,
          clamp the end of a garden hose to the metal water tube -
          then turn on the water.

          You'll see water coming from numerous small holes and vents all over the LU -

          but there should NOT be any water at all coming out of the large 7-sided muffler opening

          if there is, you have serious corrosion in the engine exhaust passage -
          possibly even the bottom of the engine block.


          • #6
            Hi fairdeal, thanks for the follow up. I need to add a little to the description of my problem.

            I have had the exhaust done on this motor and the twin for that matter. The boat is in a slip so I'm trying to narrow down all possibilities before I get it hauled.

            I feel like it just isn't getting enough coolant water at idle.If I run the boat at cruise speed, no alarm. The tell tale stream is weaker than my other motor. If I hook a hose up to the flush port It will run all day at 135F.

            Off of the hose just running in the slip....the temp raises to about 180F and thermoswitch turns "on" triggering the alarm. Temp hovers around there never gets higher. If I give it throttle the pee stream gets stronger and the temp slowly lowers.

            Waterpump was done a year ago...maybe 150 hours on it. I'm thinking something is up with it.

            Again, thanks for the input.


            • #7
              I am dealing with a similar problem except I only have 470 hours on mine and it's a T50. I removed the exhaust port cover and the anode ports. I modified a shop vac to shove a hose in the ports. Cleaned out a bunch of crud. Not 100 percent yet but much closer than my mechanics got me. I have a new cooling sensor on order.


              • #8
                Thanks for the insight Sparkdr. Anything noticeable visually about the cooling sensor? Or just a test that showed it not up to spec?


                • #9
                  When I removed it, it was loaded with crud. After I cleaned it I put it in alarm and unplugged the sensor. The alarm stopped.