DESPERADO was first repowered in 1997 when we took her original 450 hp Detroit Diesels (8-71-TI's) out, these older Hatt 53's would cruise around 11knots and run 16-18 all the way out. Slightest weight changes or sea states would not let her plane. The 8-71's when run in displacement mode (8-10 knots) would cause the turbo's and intercoolers's to need much service. Taking a page from the Hatteras 58 and 65 Long Range Cruiser we installed Detroit 6-71 N's with larger props.......We cruise at 8 knots and top speed is around 11 knots......and we burn with both engines and our 15 kw Powertech (Kubota engine)  generator about 9gph at 9 knots. Service work has been almost non existant except for normal oil changes and such. Before we did the last refit we replaced both motors and Allison transmissions to have many decades of trouble free service.