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I guess my point is that there are a number of factors that come across in practice that don't seem to be well captured in a theoretical analysis. First, look at power output at cruising speed vs. maximum power when considering which engine to purchase. I think this concept is especially important when comparing diesel to electric. Check out Yanmar's site and their ratings for the 3YM30. It puts out about 12KW at the propeller at 80% of maximum throttle. Waypoint puts out about 6kw at 80% throttle at the propeller.
Second, voltage and therefore power changes whether on generator or battery. Use 168v to get max power available when the generator is running.
Third, Waypoint is powered by 2 motors rated at 6hp per shaft. Running the numbers I observed, the max HP she is capable of producing is 22.5.
Fourth, you can run a diesel at full throttle. You cannot run Waypoint's electric motors close to full throttle or you will blow a breaker due to the surges in current caused by waves.
Finally, I do not understand why an electric motor putting out roughly half the power of a diesel at the propeller is sufficient. You need to get your arms around this issue by contacting owners of both types of boats. I would like to know how fast a diesel 410 goes at 80% throttle in calm seas. My theory is that a diesel will go faster, and the electric is significantly less powerful. However, the power difference is not noticeable at low speed and all you are giving up is top end. The electric probably has a more aggressive prop pitch so she feels more responsive than the diesel at maneuvering speeds.
I am in no way saying to abandon the theory--just look at the case study first in some detail so you can establish a baseline for your theoretical analysis. And please keep posting your results.
Brett
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