A friend of mine spoke to a reputable engine builder who stated that 4.750 stroke crankshafts were too big, and the subsequent large engines they create, won't RPM in a boat, even thought they will on a dyno.
The load on the dyno is allowing the motor to RPM, where as in the boat the load, continually gets larger as the speed increases. I wouldn't see where anything but TQ and HP would make any difference, the propeller doesn't know what is on the other side. If the motor, irregardless of size, produces more TQ and HP than it takes to drive the boat, the boat will continue to accelerate. Am I flawed in my thinking or is this more of that bogus boat theory, that doesn't wash. Matter of fact I would think the large TQ that a big motor produces would be more beneficial, since TQ ultimately is what drives a boat across the water. Chime in experts.