[re 505 and 526] they have a somewhat flimsy removeable piece of plywood along the engine compartment in the locker ... probably to control the air in and out around the engine compartment. and keep stuff from dropping into the shaft area.
There also is a semi bulkhead about 18 in. behind the sink. so the cabin is closed off from the engine compartment.
HOWEVER ... there were a couple of interim designs where the insides were original somewhat as they tried to figure out what to do.
Generally, in a knockdown the seat back helps keep the water out of the cockpit ... UNLESS you are off shore in waves. I think the elimination of the original bridge deck did affect the offshore rating as they apparently did not increase the size of the scuppers. Even with the seat backs adding ~3in. to the deck you will sometimes have water running over them as we did last weekend in ~6 ft short waves. But you only do Bozo sailing like that when racing? You know you really have a problem when the winch goes underwater, but that shouldn't be for more than a few seconds.
The hatch was originally fitted with a lock hasp, but nothing more that that molded baffle. You can always use a snap shackle instead of a lock.
