The pilot light lights fine but after holding it down as long as 5 minutes it still will not stay lite, I have replace the thermalcouple, what might this be, it is getting plenty of gas.

Mitch

It could be a defective thermocouple which can be tested with a thermocouple tester or some electric meters depending upon what you have in your tool pouch/bag.

It could be the thermocouple is not in the flame correctly and that you will have to eye ball to make sure it is in the proper place.

Thermocouples generate an extremely low electrical voltage which in turn usually holds a magnet in the open position so as to allow gas to pass for the main burner. If the new thermocouple is bad or misplaced in the pilot flame so as to not generate the voltage necessary to operate the gas valve safety the system will not work. If the thermocouple is working but the gas valve is defective then the gas valve will also have to be replaced.

All professional HVAC repair persons have the tools necessary to test these parts and by testing it is the only way to tell which parts are bad. SO if you do not have the test tools and the thermocouples are cheap enough I would try another thermocouple OR move the thermocouple into the flame more to see if that will get it to work.