What Are HINs and VINs?

Updated 12:31 PM ET, Mon November 9, 2015

Article highlights

  • The HIN is a specific format of numbers and letters designed by the U.S. Coast Guard to determine the boat builder, unique serial number, and model year or date of manufacture.
  • The VIN is a standardized format that was implemented by the NHTSA to help identify the make and year of a trailer.
  • It is important to have a good understanding of what these numbers and letters are, where to find them, and why they are used.
Are you looking for recreational toys? Perhaps, you want a tow-able boat on a trailer, or a larger boat to keep at a dock. How can you verify the actual model, year, and serial number of what you're looking to buy? Follow along as I break down the mystery of the HIN, VIN, and WMI codes.

What Are HINs and VINs?

The Hull Identification Numbers (HIN), are to boats what the, Vehicle Identification Numbers (VIN), are to cars, trucks, recreational vehicles, and trailers. HINs and VINs are required in order to register and/or title your boat or trailer. These identification numbers assist law enforcement in tracking down stolen boats and trailers, and are also necessary for insurance purposes.

What Are HINs and VINs?

What Is The Purpose Of The HIN?

The HIN has been around in some form since boats were first built. The purpose of this number was to catalog or serialize, by boat manufacturer, every boat built. Early on the HIN was a single digit, or a series of 3 - 5 digits, that indicated the number of boats built by size or model. These early boats would have had the HIN either engraved on a structural part of the boat or hand written on the back side of an engine cover or drawer.

As each boat builder made more of the same type or model, the HIN format became more sophisticated and better defined. Boat manufacturers would affix a Hull Plate to the boat identifying the boat builder, the name or model of the boat, and a Hull Number. Because this method of identifying a particular boat model and manufacturer varied according to each boat builder, the U.S. Coast Guard was asked in 1972 to create a standardized format for HINs. This allows for better tracking of the boats history including involvement in any accidents. The HIN follows a specific format. The first three characters are the Manufacturers Index Code (MIC). The MIC, was also developed by the U.S. Coast Guard and is incorporated into the Boat Builder's Handbook, the reference source for boat builders in the United States. All Boat Builders in the United States should apply for a MIC from the U.S. Coast Guard so that their boat brand can be uniquely identified. The next five characters are the unique serial number assigned by the Manufacturer. This can be a series of letters and/or numbers with the exception of the letters O, I, and Q (they can be easily mistaken). The last four characters determine the model year or date of manufacture for the boat. The HIN must be located on the aft of the vessel in the uppermost right corner. The HIN may also be stated on the title, registration, and insurance documents.

Why Did The HIN Format Change Over The Years?

Since 1972, the U.S. Coast Guard has issued three designs to address the last four digits of the HIN. All of these redesigns are somewhat confusing, but I will try to explain. The first incantation of the HIN used the "straight date". The ninth and tenth characters gave the year of the manufacture. Therefore, 1272 would indicate the boat was built in December 1972. The next format made the ninth digit an "M". The numeric tenth and eleventh characters denoted the model year. The twelfth digit gave the month of the manufacture using letters of the alphabet. This was extremely confusing because they were not in alphabetical order: A= August, B= September, C= October, F= January, G= February, etc. So, with "M67J", M stood for model year, 67 indicated 1967, and J gives the month of May. On August 1, 1984, the U.S. Coast Guard redesigned the HIN to reflect a new standard that is still in use today. The ninth digit is a letter that designates the month of manufacture in alphabet form: A= January, B= February. The tenth character designates the last digit of the year of manufacture, and the final two characters indicate the model year.

Boats built outside of the United States will almost always have a different HIN format to conform to European standards. Commercial and Military boat also use different HIN format from recreational boats.

What Is A VIN and WMI?

If you have a boat you tow behind your vehicle, understanding how to identify the make and year of your trailer is also important. Around 1981 the National Highway and Transportation Safety Administration (NHTSA), implemented a standardized format for the trailer VIN. The trailer VIN consists of 17 alpha numeric characters which identify:

Trailer Manufacturer or Company Identifier known as the WMI
Type of Trailer
Trailer Length
Number of Axles
Model Year
Serial Number

WMI is an acronym for World Manufacturer Identification, with these three alpha numeric characters you can determine who built your trailer. Let's take a look at a typical VIN:
1MDAPAR14FA552740. 1MD is the WMI code which identifies this trailer brand as Midwest Industries. The tenth position of the VIN identifies the model year of your trailer; this can be either alpha or numeric in nature. In the example, the letter F indicates the trailer is a 2015 model year trailer. There are various resources online to determine other model years for any given trailer from 1981 forward. One helpful link is: http://www.towlog.com/html/10th_digit_of_17-digit_vin.html.


Follow these guidelines and you can quickly verify the model year of your trailer. Just remember the tenth digit is always the model year. And remember, for boats, the last two digits verify the model year. Most importantly, though, is that you need these numbers to register and title your boat and/or trailer. If anything were to happen to your recreational vehicles, law enforcement will us these numbers to track down your stolen possessions. Though they may be slightly confusing, it is important to have, and to understand, your HIN, VIN, and WMI codes.

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