Thanks everyone,

answers to Steve's questions

cover was leaking when we bought the boat. replaced cover and screws, thought that had solved the problem, but apparently not.
yes, just antifreeze over the winter
no evidence of leading at seal where pump meets engine block

did shoot some WD 40, helped some, but didn't solve the problem. could try more, but guess I should try to get a tap that fits (or a new pump)

Van