Optimax 150 is running too cold

[eltypexx]

My 2004 Merc Optimax with 170 hours on it just runs too cold i think.

Got new impeller and T.stats and poppet valve.
The temp. senders are checkt, al new.

Ym thinking of putting an heavier spring in the poppet valve, at 2000 rpm and higher the temp drops too 70F (thermostats are the 143f type)
Could this be an option for me?

Sorry for my english

Greetings eltypexx.

[staylor]

...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

[eltypexx]

Thanks Doug,

My Optimax is running great , and the Temp thing you discribe is exactly what i ment.
This is a big relief for me !

Why dont my dealer knows these thinks?
Even the distributer, thier Techn guy didnt know what was going wrong.
And told me that he never heard about it before.

Greetzz typ.

[RobShaw]

Keep an eye on your temp gauge. The thermostats generally open around 135 degrees or so. Once they open, your temps should drop as described above. If your outboard never reaches such temperature, this means that your thermostats are fouled open by a small piece of debris. Most of the Optimax's you hear about blowing up on the water are in the mornings at blast off because their motors were never warmed up properly!

[eltypexx]

Keep an eye on your temp gauge. The thermostats generally open around 135 degrees or so. Once they open, your temps should drop as described above. If your outboard never reaches such temperature, this means that your thermostats are fouled open by a small piece of debris. Most of the Optimax's you hear about blowing up on the water are in the mornings at blast off because their motors were never warmed up properly!

Isnt it strange than that when i hit the throttle the engine temp drops a lot :confused: :confused:

First run it hot, then racing it cold :D

[props4u2]

Isnt it strange than that when i hit the throttle the engine temp drops a lot :confused: :confused:

First run it hot, then racing it cold :D


That is what all V-6 Opti's do, 2.5 & 3.0L. Yours is running normal.


Lee

[staylor]

Thanks Doug,

My Optimax is running great , and the Temp thing you discribe is exactly what i ment.
This is a big relief for me !

Why dont my dealer knows these thinks?
Even the distributer, thier Techn guy didnt know what was going wrong.
And told me that he never heard about it before.

Greetzz typ.

The factory shop manual on the Opti has a very nice write-up on exactly how the poppet style cooling system works. Its not good that the tech guy is too busy to read the manual. In any event, back in the last century Merc's did not run thermostats at all and they were one of the last makers to add them. I recall buying a Mark 58 powerhead on a 1:1 Quicksilver racing lower unit that actually ran at about 130 degrees at idle, dropping down once you revved the motor up- with no stats. I pulled the lower unit and discovered a previous owner had drilled some holes in the main water tube up to the block. This caused the motor to run warm at idle, yet the higher flow at high speeds dropped the temp down- just like today's Opti. I checked with a few other racers and several said that this was an old trick to keep the race motors from fouling plugs at idle/low speeds before a race started. This was in the days of running gas/oil ratios in the 12:1 range.
Doug

[j_martin]

Isnt it strange than that when i hit the throttle the engine temp drops a lot :confused: :confused:

First run it hot, then racing it cold :D

As I muse about this a bit, I realize that if you consider the resistance to heat transfer through the cylinder walls, and the amount of heat being generated at different throttle settings, the temps at the actual operating parts of the engine are probably staying pretty even.

Darned ingenious, I say.

John

[eltypexx]

So happy to read is nothing wrong with my motor.

It is still a bit strange but I think now that it must be just so.

Thanks

[hsbob]

on the other side be sure to warm the motor up before wot. the opti suffer from cold seasure[sp] if they are not warmed. likewise my 200xs opti runs at about 138. the 180 temp is not needed for the direct injection where the air atomises the fuel and not the heat as in efi.

[props4u2]

I take it your 200xs runs 138 @ idle then drops to cold @ wot like all I've ever seen???


Lee