Hi Josh,
I have a model 17 in my shop at this time and it has a Perkins diesel. If you get the serial number off of the tongue and call Morbark, they can tell you what engine the chipper had when it left the factory. I'd be careful as my customer needs an exhaust manifold and Perkins is no longer making them. When you purchase an older chipper, you risk the chance of not being able to get parts for it when needed. For example, Altec bought out Woodchuck Chipper Corporation and they are no longer supporting chippers that are 20 years old or older.
Hope this helps!
Dave
Global Equipment Exporters
770-420-6400