What engine does my boat have?

I was just given a boat, and I'm not sure what engine it has. I didn't get a good look at it because it's full of leaves and whatnot, but the previous owner says it's an inline 4-cylinder. It's a Mercruiser inboard. The year, he believes, is 1984. It's a 17-foot fibergl tri-hull deck boat. He said he thinks it *may* be a 230, and he thinks it's supposed to be around a 200-horse engine. Guesses?