Yamaha Waterproof Cap YF1-89616-05-20. Overview. The Yamaha YF1-89616-05-20 Waterproof Cap is a genuine original equipment manufacturer component designed to protect electrical connections and sensitive components from moisture, dust, and debris. This cap helps seal exposed connectors or ports, preventing water intrusion that could lead to corrosion, electrical issues, or component failure.. Maintaining proper protection of electrical systems is essential for reliable engine and equipment operat