- Stock #257120 - 1987 DONZI COMPLETELY REFURBISHED (383 STROKE ENGINE WITH 35 HOURS) BRING OFFERS Donzi is known for its line of performance racing boats and this Z 21 is no different. If you are ready to get from point A to point B in a fast amount of time, this is the boat for you. Powered by a 350 hp Mercruiser engine, this Donzi can move! According to the seller, the cruise speed for this Z 21 is 30mph. This Donzi Z 21 features a stereo system with 4 speakers and volume control at the helm. The seller has added trim tabs with controls and updated the hydraulic engine hatch. There... read more