Master's licenses are issued in 5 year increments so you must be on your 4th issue.
Well that is something Roger. Either the test was different back then or you are one smart individual! I had been on boats for 25 years when I began the process of studying, and what I knew was about 10% of what you needed to know to pass the exam. You must score a 96 or better on the Rules of the Road portion and that is pure memorization though 50 questions. The other sections have minimum scores as well.
There is just a TON of material to understand. The different light configurations for subs, fishing vessels (more than one type), tugs, barges, bridges, locks (several types), pilot boats, vessels greater than 50m in length, etc., etc., etc. The 20 or so primary structural components on tanker ships by name and position, the names of the dozen or so block and tackle configurations and whether they are rove to advantage or disadvantage by name, firefighting techniques and chemicals, cargo loading and weight, balance, and C.O.G calculations, all the clouds identified by altitude and shape, all the planetary winds and their position relative to latitude, all the types of fog and how they are formed, all possible navigation questions and techniques including visual range calculations, non-tidal current calculations, loran calculations, all types of ships systems and navigation systems, how to maneuver in heavy weather, determining the relative direction of hurricanes and the best way to navigate through them if you must, the 25 or so knots and their uses by name or picture, and last but not least....CFR (law) reference questions. These were just a few things off the top of my head. I could go on and on but there are some things that are really detailed and obscure.
There were 4 tests and my total test taking time was about 6 hours. I was not the last person to leave the room. In fact I think I was among the first few to finish. It is simply impossible a person would know all this material from recreational boating experience. I already had my Private Pilot's license when I began the process and these exams were just a completely different paradigm in terms of the amount and difficulty of the material.