This is the top of the Diesel Engines facing the bow. You can see the valves. In case you are not very technical a Diesel engine doesn't use spark plugs. It ignites the fuel through a high compression rate. The Olive Green is the Rods to the Engine. Notice the shirt on the left. That is about how much room is between in the center of the Engines. I would have hated to be depth charged in the small of an area. Also think of the heat of the engines and imagine it in rough seas.