The last two digits on the registration located on the transom should be the year if before 1984.
The decoding of HIN numbers changed in 1984, it was still the last three digits but before 1984 it was a two digit year followed by a letter to indicate the manufacture date like 78A would be a a 78 model built in August of 1977.
It should be three digits for 1984 and on but they used a number for the month not a letter.
