Four stroke engine having blow-by ventilation system and lubrication system

The present invention relates generally to a new engine for use in, for example, personal watercraft. In particular, the present invention relates to a new four-stroke in-line engine that was developed with a view to the future stricter environmental and emission regulations. The engine has a blow-by ventilation system for separating lubricant that may be entrained within blow-by gases. The engine further includes an improved lubrication system. A four stroke internal combustion engine is disclosed having a lubrication system for circulating lubricant within the engine. The engine further include a system for separating lubricant from blow-by gas within the crank case.