Air carrier pilots reported they refused an aircraft that was indicating non-normal vibration in the right engine.

Narrative

We were reassigned to ferry Aircraft X from ZZZ to ZZZ1. We flew the aircraft in the day before on Day 0 on MEL XX and we saw no engine vibration indications the entire flight. The next day a previous crew refused the jet due to engine vibration indications. We spoke to maintenance; dispatch; and the dispatch duty pilot and made the decision to proceed with the ferry flight from ZZZ to ZZZ1. Shortly after starting the right engine it began to show excessive engine vibrations which required us to reference our QRH. The QRH directed us to secure the engine in idle so we returned to the gate; entered an logbook; and refused the aircraft.The MEL is vague and also the fact that we flew the jet the previous day on the same MEL and the vibration indications were completely different.A more clear MEL stating that the vibration indications aren't accompanied by any other abnormal engine indications or actual physical engine vibrations. Additionally the part could have been flown in from ZZZ1 and changed so crews would not be put in a position to be asked to disregard a QRH procedure.