Found this sight about many types of electric motors to power boats

[videorov]

This site looks to have good information.
Looks like there are alot of companies starting to make electric motors
for sailboats and more.http://www.boatdesign.net/Directory/Propulsion/Electric/

http://sailingwaypoint.com/

Good reading about what is going on in the electric motor world for sailboats. With cost of fuel going up and just to have the motor on
and no noise would be nice.

[Eleven]

Just had a brief look at http://www.boatdesign.net/Directory/Propulsion/Electric/.
20 knots cruising, on the ocean, what sort of springs does it have?

Sample:
Africat Marine
Manufacturer of the Africat 420 power catamaran, a luxury, high-performance 42ft cruising power cat with a cruising speed of 20 knots. Headquarters in Fort Lauderdale, Florida, USA. (Added: 19-Dec-2005 Hits: 3828)
End Sample

But then there's also data on a 90% efficient motor that makes coupling to a diesel genny work well. Put the genny where it's quiet or close to cg and put the motor(s) on retracting legs. It's an option.