2001 Johnson Overheating Alarm

Discussion in 'Outboards' started by byob1985, Jul 17, 2013.

  1. byob1985
    Joined: Apr 2013
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    byob1985 Junior Member

    Hi Folks,

    I have a 2001 Johnson 50HP with good compression (135# and 137#). Just put in new plugs, water/fuel separator and lower unit oil. Mixing the oil between 50:1 and 44:1.

    Ran the boat in warm water (89-91 degrees) this weekend and the overheating buzzer went off after a short ride on plane (10 minutes). The impeller seems to be working fine as water is exiting the cooling system via the side tube.

    Manged to get back, by nursing it at low RPMs the whole way, but anything close to plane would trigger the alarm. I felt the head at the dock and it didn't feel too hot. The lower unit was a little hot, but not scalding.

    Could it be my alarm is acting up? How would one test this?

    Thanks!

    Scott
     
  2. powerabout
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    powerabout Senior Member

    remove it and put in hot water with a thermometer and check what temp it closes the circuit
     
  3. swade
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    swade Senior Member

    maybe the sending unit? I'm not familiar with johnsons. But when i'm wondering what my motors doing i ping the thermostat area with an infrared thermoter...it seems reasonably close by checking docs,but guess depends on how the thermostat is buried on a particular motor.
     
  4. powerabout
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    powerabout Senior Member

    I forgot yours is a 4 stroke yes?
     
  5. PAR
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    PAR Yacht Designer/Builder

    Yep, Powerboat has it, check the opening temp with a thermometer and compare against spec. It wouldn't be the first sending unit to take a dump.

    You also could have an impeller issue. You might have a good stream at idle, but the pump isn't pushing enough water at higher RPM's. When was the last time the impeller was changed? Lastly, check for blockages, by removing the inlet grill(s).
     
  6. byob1985
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    byob1985 Junior Member

    It's actually a two stroke. I just bought it used, so not sure when the last time the impeller was changed.

    Leaning towards the impeller theory, as there's actually a weak stream at idle and it increases w/RPMs. Actually often it won't initially stream at idle unless the motor is trimmed to be completely vertical, then it will stream at any trim.

    So you are saying I should fiddle around and find where the alarm lead goes into the engine and remove it to test? What would be a proper overheating temp for such an outboard?

    Thanks!
     
  7. CDK
    Joined: Aug 2007
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    CDK retired engineer

    If this is a Johnson 50VRO the alarm may also come from the oil injection pump. A lot of owners disable that pump because the only thing wrong is in most cases the alarm circuit itself and parts are not on the market, just a complete, expensive pump.
     
  8. byob1985
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    byob1985 Junior Member

    CDK - not sure if it's VRO, but I premix my fuel, so don't think there is an oil pump or corresponding alarm. Then again, I am unfamiliar with Johnsons, so I could be miss reading your reply.
     
  9. CDK
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    CDK retired engineer

    The VRO engines have a big black device right of the carbs, with a lot of hoses attached to it. Owners who disable it leave the pump where it is because it is needed for fuel as well, they follow internet instructions and should pull a plug or cut a few wires. These are the ones powering the buzzer.
    If you have just a small pump next to the carbs and a lot of empty space, you have probably an original non-vro engine.
     
  10. powerabout
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    powerabout Senior Member

    can you post the model number on the tag or take a photo as a 2001 50 is a 4 stroke
     
  11. powerabout
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    powerabout Senior Member

    the thermostat on a 2 stroke is 143 F
     
  12. byob1985
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    byob1985 Junior Member

    I can't get to it until next weekend unfortunately, so will get the model number and determine the VRO status then. Thanks for all the ideas and help so far!
     
  13. byob1985
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    byob1985 Junior Member

    Pics of Engine

    Here are the pictures of the outboard to ID whether it's a VRO or not. Now the alarm kicks on when engine is started cold (w/water circulating), so I don't think it's the overheating alarm, or it could be really off.
     

    Attached Files:

  14. CDK
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    CDK retired engineer

    Not a VRO model, also not 2001 but several years earlier.
    Look for a tan wire (without stripes) that is connected to the thermal switch. If removing the wire silences the alarm, the switch is defective.
     

  15. byob1985
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    byob1985 Junior Member

    Thanks!

    Thanks CDK! Interesting the seller told me it was a 2001, but clearly didn't know or knew otherwise...

    So the tan wire should be near the carbs somewhere?
     
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