I used to rivet steel with 1/4" drive pin aluminum rivets and have tightened loose rivets in boats. But to build a boat and rivet it, not.
The drive pin aluminum rivets work really slick and will hold forever. They come in different sizes and lengths, and may be what would work good for you, D. An air rivet tool works really slick for them.
I bought some at one of our local welding and supply stores and use them at home.
While I worked in a GE switchgear factory for 4 years, we used them all day and I have never seen one of those rivets fail. We used 1/4" rivets and 1/4" holes were drilled for them. I strongly suggest using an air hammer tool. You can use a regular hammer but might inflict some dents and it will take much longer to drive the pins with a hammer. The pins are designed for air hammers.
The head of the rivet is rounded and smooth, and will fit flush with the surface of your aluminum. They would make a nice outside smooth surface for your boat.
The mentioned rivets spread 4 ways evenly as the pin is driven and would be a faster way of riveting for most folks but you should find some and make up your own mind as to if you want to use them.
