It is not a 2001. That serial number belongs to a motor of model year 1994. S in this case stands for the shaft length, short, and is not the letter for model year. The serial span for the 15D model in 1994 is from 115096 to 124184. This engine with nr 116288 fits right in there..
Depends where I’m the world you are. The letters mean different years for the US and other areas. If you have a picture of the engine, I could likely tell you within a year or two. I’m a total Yamaha small 2 stroke geek, haha.