IMPORTANT NOTE: It’s critical that a small portion of the engine exhaust cooling water flows freely out of this “pisser” vent pipe when the engine is running. If it is plugged there is a very strong chance that when the engine is shut down, the residual heat from the engine will create a vacuum and suck water into the crankcase through the raw water intake. Keep a close watch on this fitting. Especially for spiders and mud wasps because they love to get into small spaces like this!