Mark P
Senior Member
I am looking at the Helmsman 38E with a 250 HP Cummins QSB 6.7. In published test ratings on this 30K Lb semi-displacement vessel, at 1K rpm it does about 5.8 knots, at 1500 rpm, it does 7.7 knots, at 2000 rpm it does 9 knots, at 2500 rpm it does 11.4. At WOT it does 14 knots. Not knowing how loaded the boat was, what could I reasonably expect the speed characteristics to be if I went with the 380 HP engine instead of the 250 HP? Trying to figure out whether the additional engine cost is worth it. Of course, fuel burn really goes up with each rpm increase, but setting that aside for now, any thoughts would be appreciated.