Q: My water heater runs out of hot water after about 5 minutes.
A: If this is happening there is a possibility that the dip tube has fallen apart or the gas valve is too slow to react and the temp is low. A failed dip tube is a fairly common occurance especially in a group of water heaters from the early 90's and late 80's. If it is a sudden occurance. Ask your self this, Is the water heater over 20 years old? If so it probably should be replaced. The newer units are more efficient. The power vented units that look like the one you took out but with a pvc vent that blows the air out the wall, are not very efficient and do take on average more air out of the house while running.
Replacement of a thermocouple is a regular occurance but should happen less than once every 5 or 6 years. If it is more then there is an issue with the pilot or gas valve.
The newer water heaters especially need to have the dust kept from the burners and should have the area clenaed around them regularly. Dust can cause pilot outages and safety limit trips before a year is up. The newer models come with a screen to filter dust. This is very fine and pluggs up quickly depending on the environment. Call Mr Heat and Cool for water heater or gas dryer clenaing. 231-955-8780
Dryer fires and water heater dust fires are common occurances through out the Nation.