.. or your life....years ago when I was working in Norfolk, VA, I spent some time at Norshipco, which is one of the marine refit yards there. They seem to specialize in medium size commercial vessels, although I have seen them haul passenger liners etc in their floating drydocks. Anyway, they had pistons in their machine shop they were reconditioning which were from marine diesels which run on bunker oil. The pistons were three feet across, made of aluminum, and the recon process consisted of building the piston up with welded metal and then remachining it in a huge lathe. The ring lands were easily an inch square. They also had a lathe that they used for turning propeller shafts- the lathe drum was five feet across and the process of turning a prop shaft for a medium size ship took about a week or two. I can't imagine engines on that scale.