Silicon Bronze All Thread
Variously known as "Ready Rod", "Allthread", or "Threaded Rod", this stuff belongs in every boat builder's shop. Each rod is a box of assorted bolts as you can easily cut them to any length required with a hacksaw.
Silicon Bronze is one of the most corrosion resistant materials around. It is idea for boats that are used in salt water and a good idea for boats that are used in fresh water.
Buy a couple of rods and a selection of nuts and washers so you will be ready when your boat needs repairs - in fact cut off a few lengths and carry them in your boat's repair kit.