I had a guy give me a big gas engine. Trying to find out what size it is. I'm pretty sure it is a zenoah engine, because it says zenoah on the spark plug. There is a tag on it that says G4D and no. 066482.It also has a walbro carb on it. The prop hub has six bolts for attaching the prop.It has a magneto in the back of the engine that is covered by a red cover. Any help would be greatly appreciated.