Valve timing control for marine engine

Abstract

A marine drive has an engine, a propeller and a transmission to switch the propeller between a propulsion position and a non-propulsion position. The engine has a combustion chamber. An air induction system communicates with the combustion chamber through an intake port. An exhaust system communicates with the combustion chamber through an exhaust port. Intake and exhaust valves move between an opening position and a closing position of the intake port and the exhaust port, respectively. Intake and exhaust camshafts actuate the intake and exhaust valves, respectively. A VVT mechanism changes an actuating timing of the intake camshaft at which the camshaft actuates the intake valve. An ECU controls the intake camshaft to set the actuating timing at a generally optimum timing. A transmission position change operation sensor senses that the transmission is under operation and sends a signal to the ECU. The ECU controls the VVT mechanism based upon the signal to move the actuating timing away from the optimum timing. Otherwise, a transmission position sensor senses that the transmission is in a neutral position and sends a signal to the ECU. The ECU controls the VVT mechanism based upon the signal to bring the actuating timing to a generally fully retarded timing.