We are looking at a new dinghy this year. I am more or less settled on a Highfield CL310 http://www.highfieldboats.com/classic-310/# It is aluminum hull and weighs 132lbs. Max outboard size is 20hp. Looking at the 15hp and the 20hp Merc they are identical displacement and weight. I have run into this before where the lesser hp motor is just a tuned down version. The difference in price is $500. Do any of you know if I will really notice the extra 5hp?.... can you tune up the 15hp to 20hp if you wanted to ?