Yamaha - Tube, Water Cooling System Tube 6D0-44362-01-00. Overview. When you're working on Yamaha outboards, the cooling system is something you never overlook, and this water tube plays a bigger role than most realize. It's responsible for moving water where it needs to go to keep the engine running at the right temperature. I've seen engines overheat from something as simple as a worn or misaligned tube. Get this part right, and you keep the cooling system flowing the way it should, especially