Looking at a motor on ebay, owner has lots of positive feedback. It is a 1984 dt85 20" shaft. Includes the control box, wiring harnesses, ignition switch w/key. Serial #411893, model #DT-85. This motor has good compression in all cylinders. This motor started and ran very good in our tank. No problems with the idle or with throttle. This motor is ready to bolt up and go! Tilt and trim works great. The prop is also included. Price is about $1300. Does this seem OK, and how difficult is the installation process? Or should I pay someone to do the install? What problems occur if the hp rating is slightly higher than the boat rating?