Rivet size depends on rivet hole size. If you have already removed the rivets, measure the hole and thats the size rivets you need. I'd order some the next size up as well for any holes you may ding up removing your factory rivets. Just drill the hole out to the proper size and your good to go. Rivet length depends on the thickness of the two materials your riveting together. I don't remember the exact number, but you want a rivet that's something like 20% longer than the thickness of the two materials. Yes, I put a bit of 5200 on all my solid rivets and transom bolts.