Hello--I am very new to canoeing. In fact, I don't even own one yet. I'm close to buying the 15' 4" sportsman canoe with a square back. Its a 3 person canoe. Its me and my twin boys, age 5. The canoe is rated for a 4hp outboard. I can find many used 5hp motors for around $400-$500. But I cannot find any 4hps. What will happen if I put a 5hp engine on a canoe rated for 4hp? Thank you!