The steel bolts rusted thru unseen from the inside or outside. There was no signs of corrosion until the hidden part of them got thin enough to break. My boat has seen some salt but is used in 99% fresh water.
To add to my problem, when I was loading my boat on the Suwannee [Saturday afternoon], the very fast current at Branford swung the rear of the boat to a 45* angle and snapped off one of my 2" PVC guide poles that peeled off my domed Allison decal and some of my gel coat.
I am almost finished with a new system that has a vertical roller mounted on each new guide pole. I also added a new and shorter guide pole about 18" forward of the rear roller-pole to make loading in high current/wind easier. Hopefully it will work. I am waiting on the replacement domed decal from Allison and then I will repair the Gel coat.