Temps when running!

[chad202]

Mercury 250 ProXS 2-stroke: 2B533867

At idle, I always watch my temp and water pressure as the stats open and close. It controls great at 130. When up and running say 4000rpms, I have 15-17lbswp and the temp is a steady 125ish. Take it up to 5000pms, temp is a steady 120ish. Take it wide open and temp wants to run 105-110. Water temp low 60s. Is this normal.

[06 SB]

Yes. I have seen much lower temps at WOT this time of the year, like down into the 70s. There really is no published normal for anything other than water pressure at idle and WOT plus that the motor can warm up to 120+ before and after a run.

[EuropeanAM]

Perfectly normal on this model as the water flow is no longer controlled by thermostats on plane (the poppet valve is open with a straight-through flow).

Have seen temps down in the 70's at WOT when the water is really cold.

[chad202]

Thanks.

[SilverFox579]

Have seen temps down in the 70's at WOT when the water is really cold.

See that regularly here in eastern WA. I watch thermostats open and close twice via Smartcrat before gradually accelerating to cruise.

[Oneida Ranger Z520c]

Great post and information. Thanks...

[chad202]

I still wonder why/how it doesn't cold seize running those low temps and turning rpms?

[JustinNC]

I still wonder why/how it doesn't cold seize running those low temps and turning rpms?

Thats one thing I've wondered too. If the engine needs to get to 120F at idle before thorttling up, how are there not issues once the poppet valve takes over and engine temps come down? Probably why I'm an arborist and not a mechanical engineer.

[Savage]

Its a calculated rate (speed) of expansion.

Cold start Idle: Piston slowly expands and the cylinder/block slowly expands at a controlled rate via the thermostats, to the built in cylinder wall clearance.

Properly warmed up motor hammer down: Piston already expanded and the cylinder/block was expanded. Cold water comes in via the poppet valve at a metered rate, which causes the piston to cylinder wall clearance to close slightly, to an acceptable clearance. The rate (speed) of heat transfer occurs at a much slower rate, than if you started the motor dead cold and ripped it down the lake.

[JustinNC]

Its a calculated rate (speed) of expansion.

Cold start Idle: Piston slowly expands and the cylinder/block slowly expands at a controlled rate via the thermostats, to the built in cylinder wall clearance.

Properly warmed up motor hammer down: Piston already expanded and the cylinder/block was expanded. Cold water comes in via the poppet valve at a metered rate, which causes the piston to cylinder wall clearance to close slightly, to an acceptable clearance. The rate (speed) of heat transfer occurs at a much slower rate, than if you started the motor dead cold and ripped it down the lake.

Excellent explaination

[chad202]

Its a calculated rate (speed) of expansion.

Cold start Idle: Piston slowly expands and the cylinder/block slowly expands at a controlled rate via the thermostats, to the built in cylinder wall clearance.

Properly warmed up motor hammer down: Piston already expanded and the cylinder/block was expanded. Cold water comes in via the poppet valve at a metered rate, which causes the piston to cylinder wall clearance to close slightly, to an acceptable clearance. The rate (speed) of heat transfer occurs at a much slower rate, than if you started the motor dead cold and ripped it down the lake.

Gotcha.