On my B36(2002) there is a plastic panel with a covered hole in the middle through which one can connect the emergency steering tiller. Years ago the panel was held in place by four self tapping screws where under previous ownership the screw holes had become enlarged to the point where you could stand back ten paces and throw the screws in. Water leaked through one of them, then dripped onto a nearby cable inside the steering compartment. From there it ran forward into the area under the steering binnacle where it then dripped off again at the low point in the cable and into the boxed in area under the compass binnacle. Then it leaked its way past the join between the plywood cabin divider (two aft cabins) and the boxed in area and ran down the bulkhead to the inboard aft corner of the mattress which it then soaked. By chance one day I spotted a drop of water on the cable referred to earlier, and what was happening then became clear.
The sloppy screw holes were filled and the plastic panel was bolted down, but to ensure water tightness I used a small rubber grommet around each bolt where they passed between the plastic panel and the boats hull. Result was no more water ingress, well not from there anyway, and a dry mattress