This unit works great and was removed from a running motor. This unit was thoroughly tested and is guaranteed to work great without any issues. If you receive a defective part please message us and we will do everything we can to remedy this issue. Please check with your local mechanic before ordering any parts or ask us and we will do our best to assure that your marine application is well suited for the part your interested in. YAMAHA Outboard 300 Hpdi OEM ECU 6D0-8591A-11-00.