Another short term option for using electric propulsion is a removable trolling motor. It will not push your boat very fast, but is possible to dock, anchor, tour close to shore and motor sail effectively with no noise and not having to warm up the diesel. It is not possible as the only propulsion source, but can be a great add-on. The new Torqeedo 2.0 looks sufficient for our 33' boats for that purpose.
We used a pair of EM54 Minn Kota trolling motors one season on our Pearson 33 day sail charter boat. These trolling motors on brackets wore out because they are not meant to be towed or left in the water. We did use it for 1-4 hours per day for about 70 days. With both of them on, we could go about 2.5-3 kts. It was a 24v system and would run at about 30 amps, if I remember right. On two 3 hours sails with almost no wind, we used about 200 amp hours on the heaviest days. There were weeks doing twice-per day trips that the diesel was not used at all. Our docking situation is simple, so that helped. The best part was that you can just flip a switch for instant power. We were able to sail into situations that most people would use the motor and have the instant boost of power if the wind failed us. A little boost on light wind days to get to another puff of wind, or just to get some air moving over the sails really cut down on diesel motoring.
Experimenting with electric drives is fun and will drive technology. What we need is an electric motor that works on the current drivetrain when needed. Briggs & Stratton made a brushless motor (Etec?) that was about 8 hp, worked in both directions, charging and driving, and was for golf carts.
Pearson 33 (1971)
Tartan 34-C (1977)
Tartan 37 (1978)