That makes finding a home even harder with todays price of Diesel fuel
Looked at my 04 spec book and it says TBD for the 660's. However found an old boat test report that says below for 2005 model.
Test Power: 2 x 660-hp Cummins QSM Diesels
RPM MPH Knots Total GPH MPG NMPG Range NM Range dBa
1750 25.5 22.2 41.4 0.62 0.54 246 214 85
above is the best case.
600 6.0 5.2 4.0 1.52 1.32 602 523 70
750 8.0 6.9 4.1 1.94 1.69 768 668 75
1000 9.7 8.4 10.5 0.92 0.80 366 318 82
1250 11.3 9.8 20.5 0.55 0.48 217 189 83
1500 18.5 16.1 31.8 0.58 0.51 230 200 84
1750 25.5 22.2 41.4 0.62 0.54 246 214 85
2000 32.6 28.3 50.4 0.65 0.56 256 223 88
2250 37.2 32.3 64.8 0.57 0.50 227 197 91
2280 38.8 33.7 65.7 0.59 0.51 234 203 91