Yamaha - Water Return Pipe Cooling System Component YF1-58527-33-40. Overview. Cooling systems on Yamahas rely on steady, controlled water movement, and when a return line isn't right, you'll notice it fast. I've seen engines run hotter than they should just because a return pipe was restricted or leaking. The Yamaha Water Return Pipe YF1-58527-33-40 helps move water back through the system the way it's designed to. It's one of those parts that keeps everything balanced so the engine stays cool