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  1. #1

    Default 2002 Mercury 40hp efi overheating alarm

    Motor starts fine. Runs fine at idle and low speed. Soon after wot, alarm comes on, and sends the motor back to idle. Replaced the water pump on Saturday. Took boat out Sunday. Same result. Anyone have any ideas, help, clues?
    Thanks

  2. #2
    Join Date
    Jun 2006
    Location
    Treasure Coast, FL
    Posts
    135

    Default Re: 2002 Mercury 40hp efi overheating alarm

    When is the last time you pulled the thermostat?

  3. #3

    Default Re: 2002 Mercury 40hp efi overheating alarm

    Quote Originally Posted by snookwhaler View Post
    When is the last time you pulled the thermostat?
    Looks like that may be what it is. Thanks for the help. Just ordered one and will be here tomorrow.

  4. #4
    Join Date
    Jun 2006
    Location
    Treasure Coast, FL
    Posts
    135

    Default Re: 2002 Mercury 40hp efi overheating alarm

    You should make that part of your annual maintenance. They get clogged with crud, they can get stuck and the cages can actually corrode away over time.

    Also, if they have not been removed for a long time, the bolts that hold the housing can get corroded into the block making it difficult to remove in the future. So, be very careful removing the housing bolts if it's been a while.

    You can use an infrared thermometer to check temps before and after the change to be sure it's working properly.

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