Yamaha Head, Cylinder 1 - 7RH-11111-01-00. OEM Cylinder Head for Peak Engine Performance. The Yamaha - Head, Cylinder 1 - 7RH-11111-01-00 is a genuine Yamaha replacement part designed to deliver optimal combustion efficiency and maintain the structural integrity of your engine's upper end. Engineered to exact OEM specifications, this cylinder head ensures perfect alignment with your outboard's internal components, preserving compression and power output.. If your current head shows signs of wear