With a 100 hp motor, why does this guy even have his sails up?

That's pretty funny! Imagine the physics if someone really tried that... With a 300 lb motor hanging off the transom, the bow would be pointing way up in the air. Some sort of homemade tiller and throttle would have to be constructed. You'd need room for a large gas tank, starter battery which adds even more weight. Imagine the fumes, vibration, yikes!