19 Rev4 vs 21 Mirage Plus. 4200 rpm at 49ishmph with Mirage if memory serves. 4300rpm at 53 with Rev4 via GPS. A 19 Rev 4 ma have worked well but I could get alot more positive trim with the Rev4 than any 3 blade a tried. Boat is a single engine heavy hull and the 4 blade gave me the bite I needed to hold the bow up.