It could be a lot of things, low oil in the reservoir under the cowl, heat, etc.
if you want to diagnose / fix yourself, you need to get the shop service manual for your motor. It will tell you how to interpret the audible alarms and lights and give you step-by-step diagnostic process for every system on that motor. Typically the manual will run about $75. you can order a manual on this website OMC docs
, you will have to scroll through the list to find your exact model
here's a link to help you dial in part numbers when it comes to that EvinrudeParts