Cooling device in outboard engine system

A cooling device in an outboard engine system comprising an engine, a propeller shaft, a gear device for driving the propeller shaft, an engine support portion for supporting the engine, a gear case for supporting the propeller shaft and for housing the gear device, an extension case for connecting the engine support portion and the gear case, and a support member mounted in the extension case for suppressing the deflection of a depending member depending from the engine into the extension case, wherein

• the inside of the extension case is divided by the support member into an upper chamber communicating with the open air, and a lower chamber defined so that the outside water existing around the extension case is introduced into the lower chamber, a communication pipe mounted between the upper and lower chambers, the communication pipe opening at the lower end thereof into the lower chamber at or below the surface of the outside water introduced into the lower chamber, and opening at the other end thereof into the upper chamber, and an exhaust gas pressure introducing means connected to the lower chamber for introducing the exhaust gas pressure from the engine into the lower chamber, whereby the support member and the depending member are cooled by the outside water forced up from the lower chamber through the communication pipe into the upper chamber by the difference in pressure between the upper and lower chambers during operation of the engine.