Our hot water heater breaker kept kicking out so thinking it was probably the original breaker we replaced it. This afternoon again I had no hot water. I checked the new breaker and it had kicked out again. Does this mean that I have a defective water heater and should be replaced?

I think it's time to call in a electrician, you could have a problem with the wiring. May be there is an overload somewhere which keeps breaking the circuit.

Contact a reputable electrician who can test the circuits.

You're better off calling a plumber. This is his territory.
It is most likely a shorted element and most electricians are not equipped to replace them.