There actually is no act of 1927. There were Merchant Marine Acts of 1916, 1920, 1928, 1936, 1970.. There were Merchant shipping acts of 1940 and 47, etc... There were amendments to the various acts that didn't even get elaborate act name. Pulling out some archaic act without looking at the actual LAW is largely meaningless. Note in your cites Bullwinkle that you posted from the section on intercostal waters. I've already posted back in an early post on this thread, that there are separate ship size minimums depending on intercostal or coastal (interior) service, and for fishing vessels (and we're talking commercial fishing vessels here not some guy sport fishing off his yacht). Some of the larger yachts can easily top out 50 or even 75 tons.
Further, he is not in the Merchant Marine service as I already pointed out, so it's doubtful any law enacted by any of these acts applies.