The rule if thumb is 3 to 4 HP per ton, which should propel a sailboat at 2 knots into a force 5 wind when there is at least two miles from the shore. That's also a lot of power required for some hours of time. A force 5 is 18 to 24 mph with moderate waves of some length, many whitecaps, small amounts of spray. More HP would be better and I think getting that kind of power from electric motor and batteries would be too heavy for a sailboat.
Last edited by LakeSuperiorGeezer; 11-08-2011 at 02:42 PM.