200 evinrude ( has rebuilt powerhead ) starts and runs o.k. However in powering up, it has a rattle and some vibration. the prop is fine , could there be something loose in the mid or lower unit. When the engine was rebuilt the mechanic changed the water pump impellar and the fluid - but thats it in the lower unit. Could there be a bearing or bushing in the drive assembly if worn would give this effect 