[malibu795]

also an electric fan will not pull near the air(cfm) a mechanical fan with of same size will....

i'd check the on/off switch for the fan(s) and have it set right about the t-stat range..also make sure the fans come on when AC is running as well

i'd make sure the fan is big enough.. wire the fan to constant ON.
if it cannot keep temps within 10* of t-stat rating, ideally 1808 t stat=180-190 ECT by the t-stat, need a bigger fan(s) if it can.. adjust your on/off thremo switch for the fan.

also where if your ECT probe and your thermo switch probe for the fan switch at?
also how clean is the fins of bugs/dirt that would restrict air flow?

as for max temp limit... alot depends on gasket durability, coolant system pressure(high pressure higher boiling temp).. a 21# system can be ran hotter than a 16# system without over heating...

with that said... i wouldnt start to get worried till i am above 240* not that i am reccomend running that hot.. i prefer 180-200 range.

side note.. my 08 duramax has aluminum heads.. GM wont derate the engine till 250* and darn near shuts it down at 255* ECT via tuning.