The bulkheads are installed, glassed in and sealed with resin. The stringers can be seen running bow to stern. They will serve double duty, stiffening and supporting the engine and providing a vital link, engine to hull. The engine provides rotational torque to turn the propeller then the propeller produces thrust which in turn is transfered back up the shaft to the engine and through the engine mounts to the stringer and finally to the hull providing....voila, forward motion. Not unlike a sail boat where the mast transfers energy to the hull and again, forward motion.
Photo Courtesy Tom Button, Kadey-Krogen Yachts