Car is 1991 MB 350SDL. Has the above Bosch alternator, which this week sheared almost completely off the original MB alternator pulley (6 groove Serpentine). As the alternator has a Bosch "Re-man" label on it, I believe the pulley was removed from the original alternator & placed on the "re-man"... Question is: What is the proper procedure for tightening the pulley nut? The 25mm pulley shaft has an Allen wrench opening on its face & the pulley nut screws down onto this shaft. But, you cannot get a socket AND an allen wrench on the shaft at the same time to prevent stator from turning...so, what is the correct torque for this nut? Finger tight still allowed movement of the pulley...a very little more tightening of the nut made for a 'hard to turn' pulley & fan. Subsequent start-up was fine with no dash lights visible BUT after 2 minutes of running, some smoke was emitted from alternator & that baby is very HOT. So, I assume that the nut is too tight & torquing the bearings inside, creating a hard 'turn'.
Would appreciate any assistance & I thank you in advance!

The correct torque value is 60-70 N-m. There are tools available that allow the proper torque procedure to be carried out, however, at roughly 48ft lbs you shouldn't have that hard of a time holding the pulley still to achieve the proper torque rating.