Re: Springs!
Nope! What you are seeing is corroded aluminum, not galvanized. The hangers are definitely aluminum as is the whole under frame that carries the springs, axle, and aluminum fenders. Strangely enough, the main frame members are all galvanized square tube.
The bolt has peened the hole enlarged to the size of the bolt head. It was probably tight to begin with but from the working and peening the hole, it became progressively looser.
It is an easy fix because the hangers are bolted to the frame, not welded and the bolts are 3/8 steel. If they give me too much trouble I will simply tighten them until they snap off.
So, I'm going to buy or make two new hangers, and a couple of grade 8 bolts for the spring eyes. Maybe new bushings too. After all, I got the trailer for nothing and investing a few bucks simply won't hurt.
While the trailer is probably still safe for towing, now that I have identified a problem it just makes sense to fix it--before it does leave me on the road. As I said above, I wish I had seen it before I mounted the boat. I could have fixed it with less fuss.