The Boeing 747 weighs 404,600 lbs in total, but how much of that does each engine take up?
Boeing 747 can be operated with different types of engines (and in general a specific model has multiple models of engines compatible with it due to competition between different engine manufacturers). Here are some of the engines that are compatible with B747 and their weights:
GE CF6-50: 8,825–9,047 lb
Rolls Royce RB211-524G/H : 12,540–12,764 lb
Pratt & Whitney PW4000-94: 9420 lb
So as you see, from model to model the engine weight might differ and all these engines have been used on B747 at some point.