I had to smile when I read your question. Smart is such a subjective term, but having said that, the short answer is no. The vast majority of people that you will meet, including Engineers are average, few are smart (above average intelligence). Just as in any profession: doctors, lawyers, accountants, not everybody graduates at the very top of their class. That is the same for engineers. A 4-year Engineering program in collage is demanding and everyone that I know who got an engineering degree worked for it. But, when you are working on something that you find interesting, it often doesn't seem like work.
A good indication of how you might do in and engineering program is how well did you do in your high school math and physics classes. You do not have to love math but, you have to be able to do math since math is one of the tools you will use in engineering to figure things out. You do not have to get all As, but you should be able to do it and find it somewhat interesting (geometry, tribometry, algebra, etc.).
If you like to figure out how things work, if you like to solve problems, if you like to create things, you should do well in engineering. I suggest that you go online and Google engineering to get an idea of what they do (Mechanical, Civil, Electrical - and their many offshoots) and see if one of the many types of engineering appeals to you.
Hope this helps,