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  1. #1

    Default Fitting Temperature Sender

    Hello All.

    I purchased a used temperature gauge some time ago for use with my 1999 35Hp 3-cyl Johnson. Pic included, but it looks very similar to this one:

    http://www.marineengine.com/newparts...le=0175409+%3A

    Would I be right to assume:

    1. The sender unit needed is this one http://www.marineengine.com/newparts...num=OMC0174675

    2. The sender unit is installed in the location currently occupied by the brass plug in the photo (beside spark plug #2)?

    3. The output from the sender unit is wired to the gauge using the lead http://www.marineengine.com/newparts...num=OMC0174676

    Thanks.
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  2. #2
    Join Date
    Jun 2013
    Location
    Duluth Mn
    Posts
    3,193

    Default Re: Fitting Temperature Sender

    Most temp gauges are similar impedance for marine applications. Is there any info on the gauge so you can find the impedance? If the sending unit is the wrong impedance, you could ruin the gauge.

  3. #3
    Join Date
    Sep 2010
    Posts
    20,312

    Default Re: Fitting Temperature Sender

    I thought the term ---impedance -----was used in AC circuits and not DC circuits ?

  4. #4
    Join Date
    Jun 2013
    Location
    Duluth Mn
    Posts
    3,193

    Default Re: Fitting Temperature Sender

    Is it more commonly used when referring to ohms resistance in general? Consider for instance the impedance of a loudspeaker. So theoretically you are correct AC is measured in impedance ohms impedance and DC is measured in ohms resistance. I can't make any mistakes with Racer here, thanks.
    Last edited by timguy; 12-07-2019 at 11:11 PM. Reason: Typo

  5. #5

    Default Re: Fitting Temperature Sender

    Does anyone know if the sending unit is measuring the water temp in the power head or is it just the temp of the head itself?

  6. #6
    Join Date
    Sep 2010
    Posts
    20,312

    Default Re: Fitting Temperature Sender

    Remove the plug.----Momentarily start the motor.-----See if water comes out of that hole.------On an aluminum head the water temperature / head temperature are essentially the same.

  7. #7
    Join Date
    Nov 2011
    Location
    tennessee
    Posts
    4,665

    Default Re: Fitting Temperature Sender

    Does anyone know if the sending unit is measuring the water temp in the power head or is it just the temp of the head itself?
    It will measure the water temp in and around cylinders/head, expect to see variations in temps due the dual purpose t-stat/poppet.
    Pappys Sales and Service
    Owner and Factory Certified Technician
    Former racer KDBA (Kentucky Drag Boat Association)

  8. #8
    Join Date
    Jun 2013
    Location
    Duluth Mn
    Posts
    3,193

    Default Re: Fitting Temperature Sender

    Thermostats run 145 so if everything is correct you should see temperature in that area. Your gauge may not show numbers but a cheap infrared gun is fun to own. 20 bucks at Harbor Freight. I use it for everything....even cooking.
    Last edited by timguy; 12-08-2019 at 10:26 AM.

  9. #9

    Default Re: Fitting Temperature Sender

    I visited my local Evinrude Dealer today. This is the third and final time - service has always been rubbish. Totally unhelpful to the point of being useless. I can't understand how he remains in business.

    I did run the engine for a short time this afternoon with the brass bung removed. Exhaust smoke first followed shortly by a solid water stream. But I also have a matching blind threaded hole 28TPI opposite spark plug no.2.

    I'm now thinking the temperature sender unit is supposed to get threaded into the blind hole to bottom out on the aluminium head material. And a temperature pressure nipple is intended to be threaded into the water jacket threaded hole.

    Does this sound correct?
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  10. #10
    Join Date
    Nov 2011
    Location
    tennessee
    Posts
    4,665

    Default Re: Fitting Temperature Sender

    Use the water one...….
    Pappys Sales and Service
    Owner and Factory Certified Technician
    Former racer KDBA (Kentucky Drag Boat Association)

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