I've been thinking about using electric for auxiliary power for a while. My latest thought was to use a saildrive lower end and attach an electric motor. I'm thinking there is probably a saildrive unit out there with a blown engine that I can get for a reasonable price. In my search for info I found this http://www.sillette.co.uk/elect_saildrives.pdf I sent Sillette an email and haven't heard back regarding pricing but I'm sure it's too much to spend on my $2700.00 1968 E23.
So to your question Loren, any lower unit that works, has a folding prop and the smaller the better. Do you have any ideas on brands/models?
Here is a newer site about a sailboat with electric propusion. If nothin else, it is interesting viewing and reading.
Since your boat is not too large, I wonder if a large "trolling motor" on a bracket would be a good experiment -- a fisherman might buy it if/when you decide to sell it later. This might be a good way to gain real-world experience in thrust, amphours, etc.