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  1. #1
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    Optimax Temp issue

    2007 Optimax 250 Pro XS serial #:1B492182

    Engine reaches 172-174 before thermostats open and cool down on first start of day. After thermostats open engine operates normally. Cycling 120-131.

    After shut down engine heat soaks to 165 after long idle or hard run.

    never get over heat alarm or code. 172-174 on first start prior to thermostats open seems too high and I don’t remember it reaching that high in the past. Just wondering if this is normal.

    new thermostats, new water pump, new poppet valve. All oem components.

    should I be concerned???
    Last edited by Basshead35; 11-24-2019 at 06:39 PM.

  2. Member Bob G.'s Avatar
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    #2
    I would be concerned. Temp reading on MercMonitor?
    2006 Triton TR-21 XD, Mercury 225 Pro XS, S/N 1B287870

  3. Member
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    #3
    Yes.

  4. Member
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    #4
    Might be worth new sending units. Not very expensive. Since you are sure you are getting water through the motor. Or, if you have the service manual, it gives you a test procedure to perform before replacing, which might save you replacing something that is OK.
    2008 Bass Cat Pantera Classic
    2014 Mercury Pro XS 200

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    #5
    Powerhead or Adapter Plate Gasket. Or Cylinder head Orings. Would be my next guess.

  6. Member BlazerVA's Avatar
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    #6
    Did you clean the strainer to the compressor?i just went through the same issues you are. Didn’t know about that one.

  7. Member
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    #7
    Quote Originally Posted by BlazerVA View Post
    Did you clean the strainer to the compressor?i just went through the same issues you are. Didn’t know about that one.
    strainer cleaned and adaptor plate gasket new. Engine was rebuilt 200 hrs ago.
    New direct injectors
    New fuel rail
    fuel injectors serviced by Don Weed
    New Carbon Fiber reeds
    New fuel pumps
    New oil pump
    New water pump
    New thermostats
    New poppet


    Runs great just don’t want to damage the power head.

    Recently had a cracked crankcase cover (intake) and replaced with a used pro xs intake exact match.
    I assume the crankcase crack was due to over heat that I did have in the past...

    I will pull plugs and check for water intrusion. Would think if head o-rings had an issue that water would get in cylinder....

  8. Member
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    #8
    Also I may pull the lower unit and double check water pump install and that the pickup tube, o-rings, and gasket are in place...

  9. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #9
    Quote Originally Posted by Basshead35 View Post
    2007 Optimax 250 Pro XS serial #:1B492182

    Engine reaches 172-174 before thermostats open and cool down on first start of day. After thermostats open engine operates normally. Cycling 120-131.

    After shut down engine heat soaks to 165 after long idle or hard run.

    never get over heat alarm or code. 172-174 on first start prior to thermostats open seems too high and I don’t remember it reaching that high in the past. Just wondering if this is normal.

    new thermostats, new water pump, new poppet valve. All oem components.

    should I be concerned???

    Something here does not add up- PCM would have already activated the warning horn and logged an Overheat warning (well before 172-174 Degrees).


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
    Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
    Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor

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    #10
    Quote Originally Posted by EuropeanAM View Post
    Something here does not add up- PCM would have already activated the warning horn and logged an Overheat warning (well before 172-174 Degrees).
    I have DIACOM software and will video and show you what it’s doing. I’ll report back...

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    #11





    ebay photo hosting



    only a neutral over speed in history. All temp sensors read 59 degrees and match merc monitor at ambient temp with no erroneous reading. I will crank it tomorrow and post video of what it’s doing... with no alarm or code...

  12. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #12
    Ok... you'll have to post video to Youtube and then provide a link here.


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
    Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
    Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor

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    #13
    Are you testing on muffs, or in the lake???



  14. Member
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    #14
    Ok I figured it out. Ran on ears and pulled up the DIACOM and right away noticed the Starboard temp rising to 176. It reached 176 when the alarm went off. If that is too high then I don’t know why it didn’t flag it sooner. But this time the alarm went off. I pulled the thermostat and tested it in hot water and it was sticking and popping as it opened. When I pulled it out of hot water it stuck open. I’m assuming it was slow to open and sticking intermittently especially on first start... I noticed the thermostat was twisted as seen in the photo. I twisted the side of the thermostat to the center position and retested and it works now. Not sure how this happened. But it cycles and both temps don’t go over 140 on first start and they cycle from there 120-130...





    Last edited by Basshead35; 11-26-2019 at 04:05 PM.

  15. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #15
    Likely was binding - keep an eye on it going forward (any further problems I would replace it).

    Good catch... although I know the exact overheat temp "threshold" can vary from one calibration to another, they usually trigger before the engine hits 165 degrees (some well before).


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
    Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
    Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor