The 4 cases I mentioned earlier was the result of 4 different situations;
The open port would not have lead to a possible sinking, but a big problem was discovered cause of it. The boat, a new Com-pac 25, during mfg. all of the shavings and sawdust from the interior adjustments were laying under the inter hull liner. When the many gallons of water sloshed around, it washed all this stuff into the bilge where the electric pump plugged up. We ended up with a garden hose washing down the whole inside of the outer hull to clear it of debris before we could keep the bilge pump screen clean.
The worse situation was moving an old San Juan 29 from Mayo, MD to Annapolis, about a 4 hour trip. The new owner had the local marina redo the stuffing box. What they did was replace the packing over a rusted shaft. So while motor sailing up the middle of the Chesapeake Bay in November we were standing in ankle deep water in the cabin pumping with a hand held manual pump into the sink.
The next almost sinking was with a friend on a Balboa 26, when his young son motoring out of an anchorage cut to close to shore on a manmade flood control dam and drove the swing keel up over a stump. When the keel dropped down over the other side it cracked open the keel trunk. The electric pump handled the water till we motored 6 miles to the launch ramp where his trailer was parked. This same boat was almost lost when a thru hull popped off when he hauled it to Ocean City, MD and his trailer was parked on the other side of town.
The last, just happened when we were removing out boats from our local lake this fall. I was helping a fellow with a Chrysler 26 and when he cranked up the swing keel water started running out on the floor in the area of the keel cable. We only had a half mile to the launch ramp so no problems, have not heard what failed as of this date.