Re: craigcat replacement ss bolts
Stainless steel is just that, it stains less. It's not stain proof.
Depending on a number of factors, water composition, dampness, etc. a large number of stainless alloys will "rust' and leave "rust spots" on anything it touches. It's pretty common to see these stains on the mounting points of bow rails, cleats etc. I used nothing but 316 (marine) stainless steel on my boat.
Plastic isolators....again, depending a number of factors, water composition, dampness, materials involved, corrosion via dissimilar materials is a distinct possibility in a high percentage of "marine" applications. The situation would have to be evaluated before the determination could be made