On a vessel with a single propeller, transverse force has the most effect on the vessel when the engine is put __________.

Correct Answer: Option D — full astern

Transverse force, or paddle-wheel effect, is a function of propeller slip and torque. It is most pronounced when the propeller is under maximum load at low speeds, specifically when the engine is put full astern, as the water flow is directed against the hull and rudder.