I have experienced throttling due to CPU overheating on my G771JW and I have found a solution that fixes this.
Go to control panel - hardware and sound
Go to power options and use the high performance setting.
On the high performance setting, click change plan settings, then click change advanced power settings.
Scroll down to the drop down that says 'processor power management.'
Set both system cooling policies to active.
Then set maximum processor state to 99% on both battery and plugged in. Now the turbo won't kick in and overheat your CPU.
Click apply and then OK.
Now I run Shadow of Mordor on ultra at 40fps with no throttling on my gtx960m.
I hope this works for you 🙂