Electronic Control Unit(ecu) 6do-8591a-00-00 Yamaha 300hp 2004 Hpdi Outboard Posted on March 11, 2024 by admin It fits 2004 300 hp HPDI outboard engines. Please let us know if you have any questions or need any other parts for this engine. In EXCELLENT FUNCTIONING CONDITON. NOTE: PLEASE see included pictures. Your item will come EXACTLY as pictured.