How to Read the Hull ID Number

There appears to be four numbering schemes in use.  Dates for the transition from one scheme to the next might be off plus or minus a year, but I believe it looks something like this:

  • 1971 - 1973, No HIN, just a metal plate at the transom (inside cockpit)
  • 1973 - 1975, No letters for month built (e.g. CTYL16231074)
  • 1975 - 1984, a mysterious "M" is a part of all HIN's (e.g.CTYH9353M80C)
  • 1984 - present, Year built represented with a number (e.g. CTYH5390F697)

Model Year.  For the boating industry, the new model year starts in August.  Since 1975, the Month Built information has been represented with a letter.  In 1984 the lettering scheme was changed to make "A" represent the month of January.  Here's a look at the two schemes:

1975 - 1984 Jan = F Feb = G Mar = H Apr = I May = J Jun = K
  Jul = L Aug = A Sep = B Oct = C Nov = D Dec = E
             
1984 - present Jan = A Feb = B Mar = C Apr = D May = E Jun = F
  Jul = G Aug = H Sep = I Oct = J Nov = K Dec = L

The Model Year scheme in use between 1975 and 1984 derived the Year Built information from the Model Year and from the Month Built.  For example, a boat whose last three letters of the HIN were 82A would actually be a 1982 model year Catalina 27 built in August of 1981.  Here's three HIN's decoded:

CTYL06121172    A Catalina 27 built in 1972. Sail number 0612.
CTY

=

Manufacturer’s Identification Code (Catalina Yachts)
L

=

Model (Catalina 27)
0612

=

Hull Serial Number
11

=

Month Built?
72

=

Year Built
     
CTYL4327M79J   A 1979 model year Catalina 27. Built in October 1979. Sail number 4327.
CTY

=

Manufacturer’s Identification Code (Catalina Yachts)
L

=

Model (Catalina 27)
4327

=

Hull Serial Number
M

=

???
79

=

Model Year (1979).  August is the start of a new model year.

C

=

Month Built (October).  A=August, B=September, and so on.
     
CTYB0184H495 A 1995 model year Catalina 270.  Built in August 1994.  Sail number 0184.

CTY

=

Manufacturer’s Identification Code (Catalina Yachts)

B

=

Model (Catalina 270)

0184

=

Hull Serial Number

H

=

Month Built (August).  A=January, B=February, and so on.

4

=

Year Built (1994).  Last digit of the year of manufacture.

95

=

Model Year (1995).  August is the start of a new model year.