Serial # 3939199. Explanation; I have lately been buying older engines to "fix-up" I've been sticking to Johnny-Rudes because that's what I know. (I'm a novice) I did buy this Merc and I'm confused as there's a lever, right below the the front cowling, actually on the mount that says "troll". I can't seem to figure out what this does. Also, I can't figure out how to "lock" this engine down to run. There is, right below the mount, 2 brackets, one seems to be a tilt-up bracket, the other has two "hooks" on it like it locks down the engine with a cable (or a tube) running to it. Are these related? I would appreciate any help I can get. Fishdady