"Sailing backwards"

The Cuauhtémoc, a Mexican Navy training ship, has an auxiliary diesel engine. It's a Caterpillar D399, capable of 1,125 horsepower. While the ship is primarily wind-powered, the engine provides additional propulsion and can reach speeds up to 10 knots. The engine is connected to a controllable pitch propeller.

I don't remember the sails out..

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Why was it sailing backward at more than six mph? For now, at least, we don’t have an answer.