Years back, I spent some time at Norshipco in Virginia working as an occupational medicine doc there. They had pistons from marine diesels that were aluminum and easily 2 1/2 feet across. Ring grooves an inch square. I spent some time trying to figure out how to steal one and take it home and use it as a coffee table, but no luck.
I've seen similar videos in the past. In one of the ships in the yard at Norshipco, the starter for the ship's big diesel (actually bunker oil engine) was a Detroit Diesel 8-V92- same engine that powers a lot of fire engines etc over here. About 500 hp and 1500 ft/lbs- that was the starter motor.