I have a 1973 12 foot aluminum MirroCraft boat, which is a shallower boat than today's aluminum models. It's rated for 12 Horsepower, and a maximum total load of 575#s. I want to purchase a 4 stroke motor, but I see weight as an issue. Question is--can this boat handle a 4 stroke 9.9 hp at around 100#s? Or when it says 12 hp max, does it mean the weight of a '70s 12 hp, which was probably around 80#s? Right now I run a 78# 2 stroke 10 hp without problem...so I can stay with a smaller hp 4 stroke, but can I go up to the bigger model?