Proof Positive!
Hull Identification Numbers

by Mark DeSchane

Maybe I'm goofy! Probably, most people spend little (read that no) time considering the Hull Identification Number (HIN) on their boat. However, I look upon the HIN as a really neat little history lesson available about every boat that has one, and even about some boats that don’t! One of my recent marine surveys was of a vessel that the owner claimed was a 1972 model. The vessel did not have a HIN, as HINs were not required until November 1, 1972. By using reference materials I had on hand, I found that the model of the questioned vessel was first offered in 1972. This information coupled with the fact that this vessel did not have a HIN allowed confirmation that this vessel was indeed a 1972 model. A HIN confirms who the vessel's manufacturer is, the year it was built and, usually, the model year. It also assigns a serial number to the vessel.

Truthfully, the HIN on your boat is the most important identification mark your boat has. It positively identifies your boat in exactly the same way that a Vehicle Identification Number (VIN) identifies your automobile. The HIN is a requirement of federal law and it is against the law to remove or alter this important identification mark. When I am asked to survey a vessel, the first thing I do when I arrive where the vessel lays is record the HIN and make a rubbing of this number or take a photo of it.

As previously stated, HIN numbers were not required of manufacturers until November 1, 1972. However, many manufacturers did use their own method of identifying their vessels with serial numbers and identification marks. 
Generally, your vessel's HIN is located to starboard on the transom, in the upper corner. Vessels with no transom or open transoms, or multi-hulls, may have the HIN located on the starboard topsides (above the waterline on the hull) at the upper aft edge of the vessel. Vessels older than November of 1972 may have the HIN located on the port side of the transom or some other location such as an engine hatch. 

Most manufacturers use a HIN molding that is attached to the hull mold at the time of hull lay-up. The plate has the numbers and letters of the HIN in mirror image. The gelcoat and laminates are applied layer after layer over the HIN molding and hull mold, to completion of the hull lay-up. Then the hull is popped from the mold, the characters in the HIN molding advanced and the mold prepared for the next vessel to be built. Other manufacturers (Catalina, for example) engrave the HIN into the hull sometime after completion of the hull molding, or building process. 

There are three different HIN formats, which will be seen. Two were adopted on November 1, 1972. These two formats allowed the manufacturer a choice of using a Model Year or a Straight Year format. The Model Year format identified the vessel by its model year. The Straight Year format identified the month and year of production of the vessel. Optional as of January 1, 1984 was a new format version, simply called New Format. New Format became mandatory as of August 1, 1984 and replaced the two previous formats. Also, as of August 1, 1984, a requirement was instituted for a second hidden HIN to be concealed somewhere within the vessel. The purpose of the hidden HIN was to aid in the identification of stolen vessels. 

What do the characters in a Hull Identification Number indicate? 

The first three letters in the HIN, since November of 1972, have always been the Manufacturer's Identification Code or (MIC). The United States has had a close working relationship with Canada on this issue. At the time of initiation of MIC coding, Canada and the U.S. decided on a coordinated method of providing MIC codes. Vessels built in Canada will have a "Z" or "Q" as the first character in the MIC. Some vessels are home-built by individuals and it is possible to have the state issue a HIN for a vessel manufactured before HINs were required. In these instances, the HIN's first two characters will be the state's prefix and the last character should be a "Z". Example: a vessel, home-built in Minnesota, will have a MIC of MNZ. If you are interested in deciphering MIC codes, go to the website: and click on (Mfgers/recalls). 

The fourth through eighth characters after the MIC are the vessel's production or serial number. These numbers are used at the discretion of the manufacturer. They will likely be numerical, may simply be a series of numbers, or may contain information on the model of the vessel and its hull number. A serial number of 37051, on a 37 footer, which is hull #51, can logically be deciphered. The fourth and fifth characters indicate the model and the sixth through eighth characters indicate the hull number. 37051 on a 25 footer defies logical deciphering and may have meaning only to the vessel's manufacturer.

The ninth through twelfth characters determine which of the three different formats has been used. The first two formats, again, came into being on November 1, 1972. 
In the Model Year format, the ninth character will always be an M. This "M" identifies the HIN as Model Year format. Characters ten and eleven will be the model year. Character twelve will always be a letter and is the month of production. Why the following screw-up took place is beyond anyone's comprehension! The government, in its infinite ways of making things complicated, decided the year started in August and made the code for August "A", September was "B" and so on and so forth! So, you need to make a key to decipher the month of production for the Model Year format. 

You should consider that the production time to produce a single vessel might take longer than a month. You should also understand that Model Year and Year of Production may be different and will be different, when the new model year begins. As an example, when characters nine through twelve of a Model Year format read M80A, the vessel was started in August of 1979. What is wrong with the Model Year format? Three things; the space for character nine was consumed with the "M" designation; the screw-up of starting the alphabet in August; and the fact that the system emphasizes Model Year over production year. 

During this same time, manufacturers had the option of using the Straight Year format. In this format, characters nine through twelve are simply the month and year of production. Instead of M80A, as in the example above, the characters read 0879, “08” being August and “79” being the year of production. Simple, right?!? The problem with this format is that the manufacturer was not given the option of identifying the vessel's model year. 
Finally, in 1984, the New Format was adopted. The new format provides all of the information of the two old formats, both month and year of production, and the model year. The ninth character represents month of production. The key for determining month of production sensibly was changed so that the alphabet started with January. I.e: Jan. = A, Feb. = B, etc., etc. Character ten is the last digit of the year of production and characters eleven and twelve are the model year. So, vessels begun in August of 1984, with the New Format, read H384. The H3 stands for August 198(3) the month and year of production, and, of course, the 84 stands for model year 1984.

With this information, you should be able to look at your own boat and make some hard and fast determinations about how old she really is. You should be able to determine that the MIC matches the manufacturer. This information will also be helpful when you are shopping for a vessel, to determine where it was built and its age. If you see indications of any tampering with the HIN, be very careful; this vessel may have a cloudy background. If painting, damage, or repairs which have taken place have obscured the HIN, YOU must take care to make sure the vessel can be positively identified! With your present vessel make a rubbing or take a photo of the HIN and keep this information in a safe place so that it can be produced, if the need ever arises. By all means, if you are going to have the vessel painted or will be adding equipment to the vessel, do not obscure the HIN. Don't rely on the government owner's card, or the USCG Documentation Certificate to have the correct HIN. Government entities are notorious for having this information incorrect. Have these mistakes, if they exist, corrected. Understand the importance of your vessel's Hull Identification Number. It positively identifies the vessel as being yours!

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