I just picked up a Briggs and Stratton 5hp four stroke and tried it out. I bought it slightly used, it appears essentially new except for a little paint worn of the prop. It seems to have a lot of vibration from idle up through full throttle. Is this endemic to the motor or should I be getting it looked at. The prop is fine, it was the first thing I checked when I felt the vibration. Anyone had any experience with the Briggs? Is the vibration normal for the model?