After five or six minutes of idling, the pulley on my alternator does a wonderful job of searing fingertips. Is it normal for the pulley to get this hot?

Last night the charging system was only working at low speeds again. All joints have been checked and are good 'n tight. When cold the alternator is generating 13.9 volts. Once it got hot only 12.8 volts were measured. Measurements were taken both across the battery terminals and from Alt + (big red wire) to Alt case (which has a dedicated ground wire to auto chasis).

A Delco 12SI alternator was selected specifically because of superior cooling capacity. The alternator housing doesn't get hot but the pulley is likely transferring a substantial amount of heat to the shaft.

Could excess heat cause the decrease in output voltage at high speeds? Would it be wise at this point to seek a replacement alternator? The one purchased was top of the line NAPA rebuilt with lifetime warranty.

Many thanks for replies as usual,

Joe M in WV