I am trying to buy my sister a new outboard motor for her Catalina 27 as a gift. The four stroke motors are 128-133 lbs and available in 20" and 25". The 2 stroke motors are only 78 lbs and again available in 20" & 25". I have access to the Mercury line and for various reasons, I would prefer to buy the Mercury product. Please, what experienced advice is out there to arrive at the best motor for her? The difference in cost is not a serious consideration. I am just trying to buy the right motor for her. Are the additional features of the 4 stroke enough to compensate for the additional weight? What is the right length? Thank you for your help and input.