I'm not exactly sure what you mean.

If you can only turn the engine 180 degrees, something is wrong.

Assuming a small 2 cycle glow type engine. With the prop firmly attached to the engine, you should be able to turn the prop a full rotation, or 360 degrees. There will be compression somewhere in there and you will feel some resistance during compression, but you you should be able to easily turn the prop past that by hand.

If you remove the glow plug, then engine should turn over very easy, a full 360 degrees.