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  1. #1
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    99 optimax 225 question

    Have spent quite a bit of money on this thing during the past year. Used a respectable mechanic. Only thing not done is replace the thermostats. He noted one side runs about 10 degrees hotter than the other. What would be the symptoms from not replacing the thermostats? THE SYMPTOMS ARE... one day the motor runs great. Three days later engine starts right up an idles to the end of the no wake area. Begin the throttle and the engine starts to miss, hesitate and cannot get on plane. Stop, put the engine in neutral then reverse and rev the motor, much like you would if you were clearing hydrilla off the prop. Back to forward and the boat get on plane. Ser#0g900175. Building a strong hate for this thing. I do think this occurs after the engine/weather warm up during the day.

  2. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #2
    Just out of curiosity- are you pumping the bulb firm before EVERY engine start?

    What happens if you raise the trim about 3-5 degrees "up", and feed the trim back down as you "hammer down" (providing a little extra ventilation)?

    Thermostats could be a contributor... but it is perfectly acceptable to see a 10 degree variance from port to stb (temps). The thermostats work INDEPENDENTLY of each other.


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
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  3. Member
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    #3
    yes sir I do pump up the bulb. I feel sure I trim the engine up slightly as I start to accelerate but will give it a shot. Thank you for the tip.

  4. Member
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    #4
    Mine is a 1999 225 and behaving similar to yours.. It all started after the compressor was replaced, but I do not think its related since I'm getting the correct fuel/air pressures now. Runs fine for 15-30 minutes, then falls on its face trying to get on a plane. I've considered the thermostats too, but I've been wary to inspect them until I have a new set of gaskets (or stats themselves) on hand. I'll keep an eye on your thread and you can keep an eye on mine

  5. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #5
    Quote Originally Posted by centex492vs View Post
    yes sir I do pump up the bulb. I feel sure I trim the engine up slightly as I start to accelerate but will give it a shot. Thank you for the tip.
    Actually START with it up slightly, once the boat starts moving, trim DOWN for holeshot, then feed back up.

    Trying to make sure idle reliefs are fully above water surface throughout the entire process.


    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).
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  6. Member
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    #6
    Quote Originally Posted by EuropeanAM View Post
    Actually START with it up slightly, once the boat starts moving, trim DOWN for holeshot, then feed back up.

    Trying to make sure idle reliefs are fully above water surface throughout the entire process.
    Hi Don- just curious.. how many Idle Reliefs are on these motors? The only one I know of on mine is the one next to the tell tale..

  7. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #7
    That SHOULD be the only one. It SHOULD remain above the water's surface level (at ALL times).


    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