I have a 16' fishrite, the maximum mine is rated for is 9.9 hp. If you have a removable section in your transom you might be able to use a short shaft - other than that I believe a long shaft is required. If you are planning on running the motor in the river get all the Hp it will handle, you will need it to buck the current. In a lake mine tops out at about 6.5 miles per hour per the gps. Good luck and have fun.