deepholeinthewater, usually there is a metal plate located on the front center of the engine around the tilt pivot section that shows the model number and the serial numbers on it. If that is missing, some times on the top of the engine it self, there is a metal disk that looks like a freeze plug type insert. It has a number on it as well and can be decoded into the year and model and HP. See if you can find either of them. But also post a picture or three for us to see it and there are lots of iboaters that can narrow it down and even offer the exact info for you. JMHO