Stainless Steel 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.
18-8 Stainless Steel is not the most corrosion resistant materials around, but it won't rust and stain your boat. It is Ok for boats that are dry sailed in salt water and a great 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.