Diesel generator duty cycle

I am studying a diesel-electric propulsion system for an inland waterway boat to be sailed on the continent. This boat would have electric motor(s) powered by a large secondary battery, and the battery would be charged by whatever electricity I will find (exemple power outlet in a marina). But the main source of electricity would be a diesel generator. My project is to find the best compromise between the power needed to run the boat, the capacity of the battery and the power of the diesel generator. The way it would be used would be the following : The power of the generator would be something like 1/4 to 3/4 of the peak power required to run the boat. The battery would buffer the power so that at full power, the generator would produce part of the required power, the balance coming from the battery. The battery would be charged whenever the boat is idling or runs slowly -- an event that occurs more than often on a canal, because of the many locks to go through. In the case of high-speed sailing, the total run time of the generator would be more than the actual sailing time each day (typically we sail 6 hours, with a break for lunch). This occurs when sailing on rivers or large canals. In the case of low-speed sailing (such as in narrow canals), the generator would be more powerful than required. Remember that the power is roughly proportional to the cube of the speed, that is to say at half peak speed, only 1/8 of the peak power is required. I think it would not be a good idea to draw such a low power from the generator, since it would run with a less than ideal efficiency then. Rather, the generator would run for say one hour at full power, then wait several hours before the energy stored during this hour is spent by the propeller. Then the generator would restart, and the process resumes. I need an advice on the on and off periods that will perform best. I imagine that if the generator would be run for only five or ten minutes with maybe an hour of rest in between, it would run cold most of the time, which I think is not advisable. So what is the minimum period of time that would make the diesel work virtually without heat-up period problems? should the engine run at partial power for the first minutes, or can it run at full power from start time? How would the expected lifetime of the engine be reduced, as compared to a continuous operation? would this require a special maintenance (oil change, etc.)? Any comments welcome. Sorry for this lengthy text. Jean-Marc