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Old 21-05-2016, 07:23 PM   #1
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Optimax 150 cooling

Hi guys,

I'm runing a Mercury Optimax 150 DFI construction year 2006. I have replaced the water pump this winter and the engine is cooling too much in my opinion.

I now also replaced the thermostats. But it remains pretty much the same.

At idle he cools to 60-68 C. At 70 C, the thermostat clearly opens and the engine cools to 60 C to allow it to rise temperature again to 70 C.

As soon as I give a little gas the engine cools back to 32 C (eg at 3000 rpm) and that seems too low to me.

The only thing I see is replacing the temperature sensor.

I had never really considered whether he also cooled as low on 3000 rpm in the past .

Should anyone have an opinion about this or other Optimax navigators have experience with this, please post your opinion.

Thanks in advance for your opinions.

Stevie
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Old 21-05-2016, 07:37 PM   #2
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I think the popet valve opens around 2000 - 3000 rpm. There is a free download opti operations manual out there if you google it, if you don't have one.
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Old 21-05-2016, 08:16 PM   #3
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When we had our opti we checked & cleaned the poppet valve

From screamandfly:

hat's how its supposed to run....
...on the stats when under 1500 rpm, poppet opens by 2000 or so. When on the stats after about 20 minutes at idle speeds in gear your temp should reach a constant temp of around 145-155 on most boats. If higher, or if it doesn't reach a steady temp then the stats are clogged or sticking, or the pump impeller is worn. Once the poppet opens, the temp drops radically, down to just about what the water outside the engine is at, plus 5-10 degrees. This is the way Merc wants it to run, so I do not recomend playing around with the poppet. I've got an '02 150 Opti, purchased new, and have seen no issues at all with the stock cooling system- the motor seems to run just fine at all times.
Doug
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Old 24-05-2016, 06:01 PM   #4
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Thanks for the replies guys, prettig sure it's the Poppet Valve staying open:

http://files.motorka.org/plm/mercury...150_175/4b.pdf

Note: If poppet valve is stuck open at low RPM, the engine will not reach proper operating temperature (run cold) and will run rough at idle.
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