Pilot on state water tank?

Question:hi i have a state water heater,the pilot will stay on for a few days then go out relight and fine for a few more days,,i have noticed that the pilot light dances around and goes form a small to a normal size flame and keeps doing this. i have changed the termocouple and its hitting the pilot lightthe burner flame is and pilot light flame are blue on bottom and yellow on top?
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Answers:
Is it a 2003 model or newer?

You are going to have problems with it.
State will not admit to ill design.
They blame the issues on the environment the heater is installed in.

I'm cooking, so I'll be constantly editing and adding to this answer.It's a long answer.
I've had to go back on most the State heaters I've installed since 2003

Oh, just a minute-----you've changed the thermocouple. Well, then, you have an older model.

Ok, I'm back,
You should remove the burner assembly and blow it with compressed air good. You don't have a set of orifice drills like most us plumbers do, so you'll have to do the best you can to clean the little pilot area.

Put in back in and check for leaks while holding the button down on the thermostat control valve. When you have lit it, check for leaks with soapy water on the burner tube also when the burner kicks on.

A little orange at the top of the flame is good. But yellow, I mean YELLOW is not. Cleaning the assembly should have taken care of that. A very little bit of yellow is passable, just not ideal.

You should have a stronger pilot now that will keep the system going.
Since you have replaced the thermocouple, the only thing left is the replace the control valve because the regulator in it is bad.
On most of them now, you cannot adjust the regulator.
If the control does turn out to be bad, it may be best just to replace the heater.

Be careful and alert.
Hope this helps.