Water Heater to Hot !!!!

Is it just a dribble that stops after a while? Thats very normal. If its constantly leaking then your thermostat needs to be replaced. Depending on the type of thermostat, you may be able to find one at Lowes or HD. I've found not much price differential between them and the RV stealerships.

Its about a 1/2 to 1 cup every time.

I had to replace the pressure relief valve this summer. As the hot water heater got up to temp the relief valve would open and it spewed water (several gallons, I'm sure) until everything cooled down enough for the valve to close again.

It was the one time I didn't have my infrared thermometer with me so I couldn't verify the water temperature, but when I ran some into a cup and put it to my lips it was far from boiling hot. So I figured it wasn't the thermostat, and replacing the relief valve fixed the problem.

I have all ready replaced it.

I'm thinking thermostats or main control board.

Did you establish an air pocket in the tank to allow the water to expand as it heats up...if not, your relief valve will weep.

Water Heater Air Pocket:
Shut off the water supply, open the relief valve until water stop coming out, close it, turn the water supply back on.
This will reestablish the air pocket in the water heater, giving the water some place to expand to when it is heated.

It had an air pocket when I replaced the relief valve. Do you think I have to create an air pocket every time I use the unit?

You should only need to establish an air pocket each time you fill the unit.
Without the air pocket the relief valve will weep, and it could weep as much as a cup or so. But the key here is "weep", not "lift".
You really need to measure the temperature of your water before going any further. It should be right around 120 degrees.

This only happens when on propane........doesn't do it on electric?

If that is the case......you need to replace the 12V DC t-stats
The normal t-stat should open when temp reaches 130*F.

They come in a set for roughly $20. Any RV Store OR on-line vendor should carry them.
Here is one on-line vendor.....LINK

Isn't there temperature adjustment dial or rotating tab on the gas control block to use to adjust the water temp?