Well, in Il-2 WM 50 works a little differently and is only associated with higher boost settings. Don't expect to be able to run 10 minutes of high boost just because WM 50 is engaged with absolutely zero consequences, especially if you're slow and turning
If you do some reading as well you will find that the max continuous operation time could vary, and be as little as 5 minutes. There was a required "cold-down" period before it could be engaged again. Engines that went to full boost for any practical length of time developed cracks and fouled spark plugs and had to be overhauled. Engines that went to full boost without the WM 50 would have seized within a few minutes.
Anyway, I did a quick run in a Bf-109, and it was a full two minutes before the "Overheat!" message appeared (it is a bit conservative, BTW). A little over 15 minutes later, the fuel ran out (I spawned in the air with 50%). There was no loss of RPM or manifold pressure throughout the time that WM50 was engaged.
So what exactly is the problem again?