I think electric is a good idea, but don't think the technology for anything other than cruising near your home port is here yet.
Think currently the most viable system is a diesel electric, with a large enough battery bank to do some manuevering, get you out of the harbor with maybe enough reserve to get you another mile or two on battery alone.
Think that system would allow for cruising, especially if you used a regen type motor.
Now if you're talking about my fantasy system, I looked into placing the electric motor/generator between the diesel engine and shaft with a clutch between them. Figure that way I could run the electric, then when I wanted, engage the clutch and use the diesel for propulsion while running the motor as a generator.
Would have the best of both worlds, instant power and convenience of the electric drive, with the range of a diesel.