Need more rivet help please...

Well from the knoledge ya'll have given me, I'm ready to start replacing rivets. What I need to know is... How do I determin what size rivet I need?? I have dial calipers but the existing rivets will be larger I guess??? Also what type/name rivet do I need. I went to a couple sites that sell marine rivets and there are so many sizes and types I was totally lost. Mabey with a little help from the experts I can get this thing floating again. Thanks for any help.

As a general rule the length of your rivet should be 1 1/2 times the dia.So when you stick your rivet through it sticks out 1 1/2 times the dia.If it sticks out a little more that doesn't hurt,but not too much because that isn't good either.The 1 1/2 times is aircraft standard.The rivet you want has a dome & is called a universal rivet,just like the ones in your boat.
Hope this helps