Is 50 watt heater too much power for a 3 gallon fish tank?

A 50 watt heater is major over kill for a 3 gallon tank, a 10 watt heater is more than enough for a tank that size. You will nuke your aquarium very quickly the first time the 50 watt heater sticks on, with a 10 watt heater if it sticks on the aquarium temp will only raise a degree or two.