I dont have a sailboat big enough to need thru-hulls yet, but on this video, they are replacing old brass ones with what looks like polypropylene or other plastic material. Is this the way it is supposed to be done on sailboats?
Start at 4:00
I have a Worldcat fishing boat
and I just replaced the plastic thru-hulls with SS. Most of the plastic ones I replaced fell apart in my hands when I took them out.