Could be a cold natured engine. Have you serviced the fuel system (filter and such) recently? Have you thought about cleaning the carb thoroughly? I am not familiar with Evinrudes but I would start with the basics. Pull the plug and check the gap, check for excessive carbon which could be caused by a rich running engine tied back to the carb. Any other ideas fellas? Hoping Cray will chime in, he has a wealth of knowledge as do other members.