This question already has an answer here:

The propellers of a front-mounted propeller plane push air back directly on a collision course with the aircraft's body. That results in zero thrust or negative thrust from at least some sections of the propeller that are close to the body, thus making the engine work harder and use more fuel as the air bounces back from the body towards the propeller.

Would it not be better to mount single propeller engines somewhere at the back of the plane, where all of the propeller is generating thrust?

marked as duplicate by Pondlife, Dave, fooot, xxavier, Ralph J Jan 25 at 16:12

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.