fryewe: everything you said seems correct, but if the log book said "Course = whatever", then that's not a compass reading. You said yourself that the compass gives an accurate indication of heading. So either the logbook was filled in incorrectly, or for some reason the navigator filled in his magnetic course instead of his true course.
s/v Laelia - 1978 Pearson 365 ketch
s/v Essorant - 1972 Catalina 27