Well..it needs to-mount as the old one does, be close to the same RPMs, same amp rating, shaft size and configuration for the fan blade...and if it has a vent tube coming off of it the new motor "needs" to be a sealed unit so water can't get in during river crossings and such. If no vent then CFM didn't use a sealed unit. CFM fan motors don't go bad very often...are you sure it's bad? Have you bench-tested it?