Abstract: An outboard motor has an adapter plate that supports an internal combustion engine, a driveshaft housing disposed below the adapter plate, and a lower cowl. A lower cowl volume is defined between the adapter plate, cowl and driveshaft housing. A lower cowl volume inlet is configured to supply idle relief exhaust gases to the lower cowl volume and a lower cowl volume outlet is configured to discharge idle relief exhaust gases from the lower cowl volume to atmosphere. The lower cowl volume is configured to cause expansion of the relief exhaust gases prior to discharge of the idle relief exhaust gases to atmosphere.

Abstract: An outboard motor and a method of making an outboard motor provide an exhaust conduit having a first end that receives exhaust gas from an internal combustion engine and a second end that discharges exhaust gas to seawater via a propeller shaft housing outlet. An exhaust conduit opening is formed in the exhaust conduit between the first and second ends. The exhaust conduit opening is for discharging exhaust gas from the exhaust conduit to atmosphere via a driveshaft housing of the outboard motor and via an idle exhaust relief outlet and a driveshaft housing outlet in the driveshaft housing. The driveshaft housing outlet is vertically located between the propeller shaft housing outlet and the idle exhaust relief outlet. A cooling pump pumps cooling water from a cooling water inlet for cooling the internal combustion engine to a cooling water outlet for discharging cooling water from the outboard motor.

Abstract: A marine propulsion system comprises an internal combustion engine, a cooling circuit carrying cooling fluid that cools the internal combustion engine, a sump holding oil that drains from the internal combustion engine, and a heat exchanger receiving the cooling fluid. The oil that drains from the internal combustion engine to the sump passes through and is cooled by the heat exchanger.