A boat has a hull, a deck having a deck floor, and an engine disposed in the hull. A top of the engine is disposed vertically below the deck floor. The engine includes a crankcase, a crankshaft, a pair of cylinder banks connected to the crankcase at an angle relative to each other. A transom extends generally vertically upwardly from a rear portion of the hull. A stern drive unit is connected to the transom and is operatively connected to the engine through the transom. In another aspect, a marine engine has a crankcase, a cylinder block, and a crankshaft. An output shaft is disposed vertically above the crankshaft. The output shaft is disposed at least partially internal to the engine. A drive, internal to the engine, is operatively connected to the crankshaft and the output shaft. A driveshaft coupling is disposed on the output shaft.