Mast step needs to be replaced and, depending upon how badly it's damaged, the bottom of the mast might need re-sleeving or building up of the step to compensate for what gets cut off to get it to undamaged material. The fixes might not cost more than $500, but our yard charges $20 per foot to pull & restep masts. The
rudder shaft seal looks like it must be letting
water in for there to be so much oxidation around there. Add maybe 1-2 thousand and change to drop the rudder and re-do it. Opening up these things is likely to uncover other items that also need attention. These boats are not reputed to be overbuilt. Are the decks all solid?
Leaks around port lights? Standing
rigging replaced since the '70's?
Engine maintained properly? OI 41's have been around since the '70's, so
keel damage from "navigational errors" involving rocks or shoals, along with
hull issues from "operator errors" involving docks or pilings are things to look for.