On my 35 the rudder post is supported at the top by a large support in the helmsman seat with a cover over it to remove if an emergency tiller is needed. So it is supported top and bottom very rigidly and the tube in between is just to keep water out, no real loads on that section. Just wondering if yours is similar. If the rudder was whacked in a grounding you never know what kind of damage could occur though so check it out good. You may also have a hose from a propane locker that goes to a through hull just above the water line, that could also be a leak source when the boat is heeled if the hose has deteriorated. Finally your manual bilge pump also exits near rear of boat. So the following could all be point of water ingress and all should be checked off in your investigation:
wet exhaust hose and through hull, electric bilge pump hose and through hull, manual bilge pump hose and through hull, cockpit drain hoses and through hulls, and propane locker vent hose and through hulls. On my boat all these exits are in the stern and hard to get at I am guessing yours is similar.
Another thing to check for, I had a through hull for my electric bilge pump crack but not break. I noticed it while waxing the hull, this fitting is exposed to the sun so years of exposure caused it to break down and fail , or it might have been a defect from the factory when new. Anyway when the pump ran it could allow a small amount of water to leak. Since this was located under the swim platform it was a nightmare to get at to attach a hose and tighten a hose clamp, no room at all under there and you are laying down working over your head, need a good contortionist. I initially looked at using a bronze barbed fitting to replace it, but the angle and length of the fitting would not allow installation, so I went with the plastic replacement, now I keep an eye on it. All those fittings are plastic in the stern, likely to lower cost and keep weight out of the boat end, and after twenty five years you may want to look at them as replacement candidates during your next haul out. All the hoses and fittings for a boat that old may need replacement. Rubber breaks down over the years due to ozone and oxidation and sunlight, etc. Vinyl also has a shelf life. Not sure what the life of marelon is but it is good insurance to upgrade this stuff before it fails completely. A prior owner of your boat may have done this so try to see if you can find out the age of this stuff if you have a prior owners phone number. At the least inspect the condition, new hoses and fittings will be readily apparent. Old ones will have crud on them or be cracks and oxidized.
