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Thread: 21V Overheating

  1. #1
    Join Date
    May 2019
    Posts
    6

    Default 21V Overheating

    I am pretty sure my 2005 21V is overheating and going into limp mode. Boat is also reading high oil pressure as soon as start up 40 psi , 1500 RPM / 70 psi. The boat will go to 180 just on start up and idle, at first i can rev it up in neutral and get it to drop, but then it climbs back up and gets to 180 at idle, and even if i rev it cant drop the temp.

    Under load typically runs great for about 10 minutes but temp stays at 170 to 180 degree, after about ten minutes then it starts to misbehave and back fire but the temp is climbing into the 190 to 200 range i think the ECM is putting it in limp mode because of temp. i can back it off and it seems after a couple minutes and it cools down it cleans up and runs right, however if i just keep the throttle in the same position it will not clean up.

    I have dry dock run the system on a water hose and water is going through and coming out exhaust.



    I have done the following things on the coolant system.

    - New Impeller
    - Changed Oil and filter
    - New Thermostat (160)
    - Check water flow from oil cooler to the thermostat seems like good flow
    - Compression check cylinders, seem good all around 130 +/- 10%
    - Placed a fuel gauge on the rail stays consistent at 60 to 80 psi, even when it is misbehaving
    - New TPS Sensor

    I am at a loss this is right after taking the boat out of winter storage by the way, which i winterized the same as i always do, and there are not any freeze plugs or anything else that i have found that would be causing this. FYI my boat has a fresh water clean out because it was ran in brackish water first couple years, i have checked it and cant find a leak there.

    I am a little concerned that my oil pressure reading to so high i am running the recommended 15W 40 oil.

    Any help would be greatly appreciated its been a difficult start this year!

  2. #2
    Join Date
    Jul 2007
    Location
    Flowery Branch Georgia
    Posts
    2,385

    Default

    Check you oil pressure with a oil pressure test gauge . GM is known for faulty oil senders .

  3. #3
    Join Date
    Aug 2009
    Location
    London, Ontario, Canada
    Posts
    1,175

    Default

    How did you check the water flow to the tstat? Just curious.
    Cold start up and your temp is 180? That’s not right. What did it used to do. It should climb up slowly to 160 or so. You could be sucking air somewhere, this will not show on a hose as the intake is under pressure. Blipping the throttle in neutral should always bring the temp down immediately to its NOT. Maybe your impeller housing seal is shot.do you have a water strainer? Did you try opening your exhaust drain to verify water is being supplied to the motor while on the lake at idle?
    2009 21v Worlds 340 Cat
    run your engine after you change the oil
    Doug

  4. #4
    Join Date
    May 2019
    Posts
    6

    Default

    tested water flow with the 5 gallon bucket test, i found the issue i believe with a loose hose clamp and sucking air on the the raw water side

  5. #5
    Join Date
    Aug 2009
    Location
    London, Ontario, Canada
    Posts
    1,175

    Default

    Quote Originally Posted by WVSupra View Post
    tested water flow with the 5 gallon bucket test, i found the issue i believe with a loose hose clamp and sucking air on the the raw water side
    Im not aware of the 5 gallon bucket test.......what is that?
    2009 21v Worlds 340 Cat
    run your engine after you change the oil
    Doug

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