I got lost in all the strange posts so far, so this may have been stated. The reason the engine is off center is most probably because there is offset in the engine mounting (right/down thrust). If this is so then the engine doesn't get mounted directly on the center and thrust lines. It gets moved over slightly so that the back of the propeller is center on the center and thrust lines. If that doesn't make sense, please say so and I'll try to explain it in English.