Water jacketed exhaust relief system for marine propulsion devices

Abstract From the Canadian patent

The outboard motor comprises a propulsion unit including an engine, an adaptor fixedly connected between the engine and a lower unit including an outer drive shaft housing a gear case, fixedly connected to the drive shaft housing and including a water discharge passage having a discharge port adapted to communicate with the water in which the lower unit is submerged for operation and an inner housing inside the drive shaft housing and spaced therefrom to define a lower unit water jacket and also defining an exhaust gas expansion chamber communicating with the engine exhaust. The inner housing includes a duct having an upper end communicating with the lower unit water jacket and into which …