Max Outboard Exhaust Temperature passing thru hub of prop

Does anyone know the max temperature at max RPM of the exhaust gases when they pass through the hub of the outboard prop? I understand that they can be up to 1200 degrees F when exiting the cylinder head but they cool quickly. Most props have a rubber hub and I believe basic rubber loses effectiveness around 300 degrees F. - this might indicate a possible temperature max.

 

It is way below the boiling point for water.

 

Temperatures are in the 150 degrees range at sustained WOT on a lean tune. If running rich, a little cooler. The hub isn't a "basic rubber" formulation either.