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Hull Identification Numbers – Some answers to your questions!


The Hull Identification Number (referred to as a “HIN number”) typically consists of (12) characters – usually capital letters and Arabic numbers with no spaces, slashes, hyphens or other marks in between the letters.

A (3) digit “Manufacturers Identification Code – MIC” is followed by a (5) character set representing the manufacturers hull serial number and… another (4) figures that will represent the date of manufacture.

So it’s going to look like this….

             “ABC followed by 12345 and then 6789”

The first three letters (MIC) will be made in block capital letters or in some cases a mix of letters and numbers (letters are most typical.) These are issued or assigned (in the US) by the Coast Guard and it identifies the plant of manufacture that is unique to the organization or it can simply represent the organization to whom it was issued.

The next four to eight numbers (depends on which manufacturer built the hull… some use 5 characters, some 6, 7 or 8. These are the individual characters that represent the unique hull serial number assigned to that hull. No two boats are assigned the same number and like the others, these too will be capital letters and/or Arabic numbers with one exception… the letters “I”, “O” and “Q” cannot be used.

The last set of numbers (usually four) are often combinations of letters and numbers that will indicate a month and year of manufacture and the model year for which the boat is built. The “date code” aspect of this set has been handled in three different ways over the years and has to be “interpreted” according to some of the following information.

Country Code – This is an optional addition to the Hull Identification Number. Manufacturers of boats have the option of adding the prefix – i.e. “CA-“ (block capitals and a hyphen) in front of the HIN number. This is a mandatory requirement for manufacturers who are exporting to another country (such as the European community) however this is not a part of the accepted mutual recognition of Hull Identification Numbers between the US and Canada.

Marking on the Hull – The HIN number is to be permanently affixed into the hull or hull member, or on a plate, such that the removal of the HIN or plate would be obvious and non-normal to the surrounding surfaces or area. No character of the HIN is to be less than 6 mm (.250”) in height and width. The HIN is to be located as follows:

On the transom above the load waterline (prefereably on the upper starboard quadrant.)

  • The starboard side at the aft end of the hull that bears the rudder or steering mechanism if the boat has no transom.
  • The outermost starboard side at the aft end of the hull, if the boat has more than one hull and no transom.

Some manufacturers had added some additional characters after the HIN but separated from the HIN by a hyphen. (Keep in mind this system is geared to work with all boats, pleasure, commercial, aluminum, fiberglass, sail, power, etc. – so the hull and manufacturer variations do take in some latitude.)


The three different numbering systems used are as follows … (newest version first) - The simplest way to figure which one your boat is using is to first identify the year you believe the hull was built. Then look for the system that was most likely in use during that time.


System 1

Most builders started using this format in January of 1985 and it is still in use today.

              ZZZ 12345 A 5 88

ZZZ - MIC code (Unique to the company that built the hull)

12345 – Hull Serial number

A – Month of manufacture

5 – Year of manufacture

88 – Model year

All of this goes with the following letter designations for each month as follows:


January – A  February – B  March – C  April – D   May – E   June – F


July – G  August – H  September – I  October – J  November – K  December – L


Character nine is the letter of the alphabet that indicates the month during which construction or assembly began.

Character ten is the last numeral of the Year during which construction or assembly began.

Characters eleven and twelve are the last two numerals representing the Model Year for which the boat was built.

FYI… it’s always a bit confusing for those boats who may be documented, registered or licensed as being a 1988 (built in December) but may not have been completed for any number of reasons until the first, second or third month in 1989. It doesn’t mean anything significant but some people want to get attached to the specific “Tuesday” when she rolled out of the shed! They’re going to have some problems with this….


System 2

Most builders used this format from the “mid-70’s” until December of 1984 and some still continued to utilize the previous (earlier) system. (Initially this system was adopted and “suggested for use” and later on it was not a suggestion by the Coast Guard but a mandatory request. That’s why some manufacturers took their own time to comply or not.)

                ZZZ 12345 G77E

ZZZ - MIC code (Unique to the company that built the hull)

12345 – Hull Serial number

G77E – Month and year of manufacture

All of this goes with the following letter designations for each month as follows:


August – A  Sept – B  October – C   November – D   December – E


January – F  February – G  March – H   April – I   May – J   June – K  July - L

Character nine is the spacer letter (G) – before the year.

Character ten and eleven are the last two numerals of the model year, which begins in August of the preceeding calendar year.

Character twelve is a letter of the alphabet indicating the month during which construction or assembly began.


System 3

Most builders used this format (on a more voluntary basis than regulatory) from the 1960’s until the mid 1970’s and some converted to the newer system ahead of others.

                ZZZ 12345 1275

ZZZ - MIC code (Unique to the company that built the hull)

12345 – Hull Serial number

1275 – Month and year of manufacture – clearly simpler than the coded system.


Character nine and ten indicate the actual calendar month (01 thru 12) used.

Character eleven and twelve are the last two numerals of the calendar year.

In this case, the date of manufacture is the month and year during which the construction or assembly began.


So there you have it… take some notes and head for the docks… you’re now armed with enough legal formality to start a good discussion and hopefully, not too many arguments!

If your hull of one of those produced for some reason without a HIN number molded into the hull but have one listed on your legal paperwork, you’re not in trouble as long as the area where the number should be found does not show signs or evidence of either being altered, mangled, puttied, ground or scraped over! In todays markets for boats, there are professional thieves who take great pains to make something look like what it’s not. A bit of careful scrutiny can determine the issues if it’s just the last four coats of hull paint that have filled in the numbers. In some cases, the numbers may be formed within a surrounding recess with the visible number itself standing higher than the background surface. This was done to permit a changeable set of figures to be cast in when the very first gel coat layer was done.

Boats without hull numbers are problems to sell and should be a problem for you to buy if you want to protect your investment. Stolen property can and will usually be confiscated meaning you paid the money, but have nothing except a “hole in the water” to sit in while the legal side is being worked out. Don’t take chances unless you don’t mind losing!


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