Sylvan has been around for years and is a popular boat here in the midwest. It's certainly not at the top of the chart when compared with Lund, Crestliner, Alumacraft etc., but it is a sound boat and will if taken care of the previous owner will serve you well. I would be more concerned about the engine condition than worrying about the quality of the boat.
My friend is looking at it. It is a 19' bowrider with a 4.3 mercruiser. I just didn't know anything about the manufacturer. The motor and outdrive is not a problem as far as checking it out. I just didn't want him to bother driving to look at if it was like say bayliner in the 80's.