I have a 1988 Evinrude 7.9 short shaft outboard motor on a 14 foot aluminum car topper fishing boat. I still have the original prop that came with the motor. Is it worth changing the prop to increase performance or is the risk of damaging the motor too great. I use the motor for a 2 hour river ride o get into our cottage and then it is used for fishing while there. Speed is fine with myself in the boat but add another person and a child and speed is drastically decreased.