Thanks to all who have contributed to this thread which should be most valuable to anyone willing to "hang in there" with the boat and facing significant refurbishment issues below the cabin sole.
My remarks concern Hull 521 which has a "half-length" engine cover) but they should be germaine to the issue of keeping the "hidden bilge" below the engine dry on many if not all of our boats.
On my boat the "hidden bilge" under the engine is kept dry with frequent inspections and "sponging" or "paper-towelling" through a 3" inspection hole cut into engine bed liner forward of the engine and slightly to port - previously described by other members. More importantly, significant water ingress to that "hidden bilge" drains into the main bilge through the passage which originally accomodated the manual bilge pump hose when the boat came from the factory. The original hose was removed and one of a slightly smaller diameter was passed from the main bilge to port under the settee then aft through the sink / battery compartment and through a hole in lazarette bulkhead to the manual pump. Admittedly, the reduced diameter of the non-OEM hose along with two necessary 90-degree elbows compromise the capacity of the manual pump somewhat and if I felt that it was an issue I needed to address I would have to grind/file/saw/curse larger passages to accommodate the larger (OEM diameter) intake hose from the bilge to the pump. But it is now the work of 15 seconds to remove the engine cover and dry out the "hidden bilge" which I accomplish every time I check the engine oil prior to getting underway or any time that I suspect that water may have entered the area.
There are several sources of water into the "hidden bilge", chief among them being any water from the companionway area which runs down the side of the engine cover into the molded retaining groove and its drain holes on either side and water from the stuffing box (resulting from my chronically delinquent maintenance / replacement) which sloshes into the cutouts in the liner under the engine mounts when the boat heels at all.
I hope that this helps all those willing to lose a little manual bilge pump efficacy in exchange for an enhanced ability to keep that "hidden bilge" area as possible.
