What will fail first, and it is invisible, is the internal liner. When I removed my engine, I discovered that the internal liner had collapsed, and was creating a serious restriction to the exhaust flow (gases+water). Another user on this blog had the exact same issue recently.
I would strongly recommend to change it if it shows its age on the outside
OK I found my post from last spring
https://www.moyermarineforum.com/for...&postcount=167