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  1. #1
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    Optimax Overheat Puzzle

    2008 115 Optimax Serial # 1b723350

    About 30 days ago I hit a sandbar and sucked up a bunch of compacted sand and shell that clogged my cooling system. I eventually got some telltale stream going but not good flow and started getting overheat alarms*. I limped back to the ramp. Changed water pump and gasket(oem parts always), was due for it anyways. Better flow but still not right and still getting overheat buzzer. Replaced the strainer in the motor.. Pretty good flow after that. Idled for 20+ minutes with no alarms...thought I was good, but as soon as put in on plane I get the alarm within 10 seconds or so. The telltale looks good and the water doesn't feel hot even when the alarm is going off.

    There is a check valve in the water flush hose between the hose hook up and powerhead. The shell had this clogged to where it would only piss on the earmuffs. I eventually got the check valve to open up but today I noticed that when the engine is running in the water there is a small amount of water leaking out of the hose attachment. If that check valve was working properly it seems there shouldn't be any amount of water coming that way. It seems it would be a very small reduction in water pressure/flow but maybe that's all it takes. Any chance that check valve is the issue? I don't know what else to try?

    *I don't have smartcraft or water pressure gauge, just audible alarm. The alarm I getting is the solid beep, and the motor reduces RPM to "guardian" speed.

    Thank you for input advice in advance!

  2. Member
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    #2
    Update:Opened up the thermostat and poppit. Both had lots of sand/shell..the poppit area was completely clogged. After cleaning and reinstalling both I took it for a water test. Still getting alarm and the telltale is actually WORSE at idle now, and the poppit and thermostat filled back up with sand and shell completely. Got it home, cleaned both again. Checked strainer-that was clear. It will piss running on earmuffs but now won't piss when hooked up to the flush adapter(which it would Friday), so I must still have blockage. I'm going to just take my tools with me to the ramp next time. Run, clean poppit & thermostat, run...until it stops getting debris in it. I think I'm making progress?? Lot's of pros on here...any advice?

  3. Member
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    #3
    You might try removing the thermostats and poppet to back flush using the flush port. Disconnect telltale hose from compressor and back flush it away from engine. You might have to do these several times to get all the crap out.
    _______

    Phil
    '09 Hewescraft ProV
    '09 150 Optimax


  4. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #4
    Going to have to remove powerhead, flush block in every direction to remove silt/sand/shells, and remove adapter plate to clean it. Pay special attention to the small (1/8") hole that supplies cooling water to the exhaust tuner.


    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

  5. Member
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    #5
    Wow..having to pull the powerhead to resolve a clog in the cooling system is a more major job than I would have imagined. If it comes to that I'll have to take it to a Merc shop. Is that kind of repair "typically" covered by insurance since it was due to me hitting bottom? I would think so but y'all would know better.

  6. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #6
    Depending on the wording of your policy, it "might" be a covered cause of loss.


    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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  7. Member
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    #7
    Ran the boat for about 45 mins yesterday. Poppet is finally running clean and I didn't get any alarms at higher rpms. I did get a singe beep at idle while tied up. Indicates running cold and the telltale wasn't warm at all, so I think it was. After running on plane for about 15 minutes I came back to idle and temp climbed until overheat alarm went off. That's the only time it did. I would NOT get the same alarm just idling around or running around. Big improvement but still not quite right. Going to change the thermostat b/c it's gone bad twice before. Maybe a poppet kit too just to cover everything. Installation seems very straightforward, but anything to watch out for? I will give props to Mercury for making the thermstat and poppet very accessible on this motor. Same with spark plugs and everything else that requires servicing.

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    #8
    Have you pulled the base under the water pump and changed that gasket? Also you can check the water passage under there for debri.
    Mercury 2002 200hp Carbed Saltwater
    OT566776
    2002 Cape Horn 22' Bay

  9. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #9
    Quote Originally Posted by feather thrower View Post
    I did get a singe beep at idle while tied up. Indicates running cold and the telltale wasn't warm at all, so I think it was.
    How did you make this determination?

    There are only two warning types, each with it's "branch" of Critical (or Non-Critical) Faults.

    WARNING HORN


    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