They have to be purchased from an authorized dealer and the dealer needs to install them as there are numerical coefficients that have to be programmed into the engine's onboard computer, the EMM, using Evinrude's diagnostic software and a laptop.
-- Travis McGee, main character in a book series by John D. McDonald
The information offered here is only general in nature and should not be construed as complete factory approved procedures, techniques, or specifications. Always use the proper service manual for your motor, up-to-date service literature, the correct tools, and have an understanding of how to proceed with troubleshooting and repair methods. If you are unsure or uncomfortable with a procedure, a situation, or a technique, enlist the services of a factory trained technician.