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  1. #1
    Member
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    300x overheating/cooling problem

    Hi,

    I'm helping a friend troubleshooting his 300X with a overheating/cooling problem.

    300X, serial: OT235944

    Engine was flushed on the gardenhose before storing for winter with no problems at all.

    First startup this spring, engine overheats and horn sound after just 60-90 sec. on the gardenhose.

    Impeller changed - OK, thermostats checked - OK, poppet valve checked - OK, but still overheating and the water does not reach the thermostat housing

    We removed the LU and attached the gardenhose directly to the water inlet pipe to override the waterpump being the culprit. Still overheating and the water does still not reach the thermostat housing.

    But we discovered that water pours out of a hole between the two large exhaust ports (see image below), and if we put a stick against the hole and closes it, water rises to the thermostat housing immediately.

    Could it be a blown seal, corrosion in the adaptor plate or ... ?

    Can you help me with this problem?

    Best regards
    Martin

    20190421_085503.jpg
    Attached Images Attached Images
    Thanks

    /Martin

    Askeladden 565 Wasper
    Mercury Optimax 225

  2.  
  3. Member
    Join Date
    Jul 2004
    Location
    Penn PA
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    #2
    Need to know EXACTLY how much water pressure the garden hose has, while it is hooked up to the motor.


    Don't take others for granted, show appreciation, especially for those willing to help daily, without a financial gain.
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  4. Member
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    #3
    Quote Originally Posted by Savage View Post
    Need to know EXACTLY how much water pressure the garden hose has, while it is hooked up to the motor.
    I will check that.
    FYI the motor has been flushed with this hose after each trip for several years without any problems.
    Thanks

    /Martin

    Askeladden 565 Wasper
    Mercury Optimax 225

  5. Member
    Join Date
    Sep 2016
    Location
    Denmark, Europe
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    #4
    ...Is that a drainhole (marked on the pic. ), or what is it?
    Waterpressure on the hose should be able to keep the engine ‘cold’ enough, if the motor has been flushed with the same hose as Martin mentioned before?
    Precent Boat:
    Campion 565 / Mercury 300X

  6. Member
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    Jul 2004
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    #5
    The hole marked is a Cooling Passage for the Lower Unit, above the passage is a strainer that can only be inspected by removing the powerhead and adapter plate. The strainer is also a restrictor and must be intact, or water pressure at Idle will be low.


    Don't take others for granted, show appreciation, especially for those willing to help daily, without a financial gain.
    "Congratulations you just made the List" Help will always be offered to those NOT on the list.

  7. Member
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    #6
    Quote Originally Posted by Savage View Post
    Need to know EXACTLY how much water pressure the garden hose has, while it is hooked up to the motor.
    Savage:

    The garden hose delivers 4 gallons per minute.

    Today we tested the motor in a water tank, but engine still overheats.

    I found some images of what is supposed to be original 300x tuners, they have a fitting installed in the square hole. please see attached.
    Could it be too much water is dumped through the square hole due to the missing fitting?

    We really appreciate your great help, thank you very much.
    Attached Images Attached Images
    Last edited by prepsdk; 04-23-2019 at 04:47 PM. Reason: misspelling
    Thanks

    /Martin

    Askeladden 565 Wasper
    Mercury Optimax 225

  8. Member
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    Jul 2004
    Location
    Penn PA
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    #7
    You gave me the flow, not the pressure.

    Possible, the fitting is a restrictor.


    Don't take others for granted, show appreciation, especially for those willing to help daily, without a financial gain.
    "Congratulations you just made the List" Help will always be offered to those NOT on the list.

  9. Member
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    Sep 2016
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    Denmark, Europe
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    #8
    Forgive me Savage, just one quick question but how do you messure the pressure?
    Last edited by Sebber2306; 04-23-2019 at 10:46 PM.
    Precent Boat:
    Campion 565 / Mercury 300X

  10. Member
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    Nov 2011
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    426
    #9
    Quote Originally Posted by Savage View Post
    You gave me the flow, not the pressure.

    Possible, the fitting is a restrictor.
    The pressure is 40 psi and it's a 1/2" garden hose.

    Is the fitting/restrictor factory fitted?
    Thanks

    /Martin

    Askeladden 565 Wasper
    Mercury Optimax 225