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Hull Identification Numbers

Confusion over model years, especially on outboard engines, can frustrate buyers. Here's how to find that info on the products themselves.

Hull indentification number

Photo: Mark Corke

General Motors introduced planned obsolescence in the 1920s as a way of discerning one model year from another, in order to convince the public that buying the latest model car was fashionable, if not exactly necessary. The tradition set by GM survives today. Eventually, consumers began to rely on the model-year change, which usually happened in the fall, to assure that they were getting the latest and greatest. Car buyers still eagerly anticipate the newest technology, and dealers often offer deep discounts to move out last year's models.

Manufacturers of other big-ticket items, such as boats and outboards, followed suit, hoping to convince buyers that the newer the boat, the better the boat. For years, U.S. Coast Guard regulations required boat manufacturers to use August 1 of the previous year as the cutoff date for the next model year. For example, a boat built in September 2011 could be called a 2012 model, but if it was built in July, it had to be sold as a 2011.


When buying a used boat, take a rubbing of the boat's HIN ­using a pencil and paper to ­ensure it matches the seller's ­documents.

In 2012, boatbuilders petitioned the Coast Guard to change the date to June 1, allowing for an extra two months of production to still be labeled as next year's model. Manufacturers argued that because of marine production schedules, which, unlike automaker schedules, tend to fall at erratic times throughout the year, they needed to have more flexibility in designating the time span of their new model year.

The Coast Guard agreed to make the change, permitting a couple of months of last year's boats to be called this year's.

Fortunately, it's fairly simple to find your boat's build date. (See "HINs By The Numbers" below) The information with the boat's model year is contained in the hull identification number (HIN), which is a label permanently affixed to the boat. The number includes a date assigned by the builder. This date is technically not the date of manufacture; rather, it's the date on which the boat was certified by the builder to meet Coast Guard regulations.

HINs By The Numbers

A typical hull identification number (HIN) consists of 12 letters and numbers, as in ABC12345D404.

Here's what the letters and numbers mean:

ABC: This is the U.S. Coast Guard-assigned manufacturer identification code (MIC). Go to the USCG Manufacturers Indentification page to access the Coast Guard's MIC database.

12345: This is the serial number assigned to the hull by the manufacturer. This may be a combination of letters and numbers. The letters "I," "O," and "Q" are excluded because they could be mistaken for numbers.

D: This is the month of certification, indicating the month in which construction began. "A" represents January and "L" represents December. In our example, "D" means April.

4: This is the year of certification. The number is the last digit of the year in which the boat was built. "4" in this case designates 2004.

04: This indicates the boat's model year.

Some boats, especially large ones, may be on the floor for months before completion (even straddling the June cutoff date), while others may be finished in a matter of days. To be consistent, the Coast Guard uses the date the manufacturer says the boat meets federal regs. Once the HIN is assigned and affixed, that date becomes the boat's model year, regardless of when it was actually finished.

Once a HIN has been put on the boat, it can't be changed without permission from the commandant of the Coast Guard, which rarely happens. New boat buyers should look at the HIN and verify that the boat in which they're interested actually belongs to the model year that the dealer claims for it. Used-boat buyers should also decipher the HIN and make sure it matches what the seller and paperwork state.

What About My Engine?

Outboard motor
The month and year of engine manufacture can
usually be found on a sticker near the engine's
serial number.

The Coast Guard has no model-year regulations for outboard engines, making it harder for consumers to determine the year in which they were built. In 2007, Yamaha stopped designating model years for its outboard engines entirely. Though the reasoning is sound, it creates a challenge for consumers.

Unlike cars, in which engines are built into the product, a selection of engines usually can be fitted on outboard boats. Dealers have struggled for years to make sure that the engines bought from an engine manufacturer during one year get sold that same year on new boats.

If a boat on the showroom floor comes with a 200-hp engine but a buyer wants a 250-hp engine, the dealer may have to order the bigger engine and keep the smaller one in stock. If it takes a couple of years to finally sell that 200-hp engine, a buyer may be reluctant to buy it if the model year isn't current, and the dealer may have to subsequently discount it. Buyers typically want a 2017 engine, for example, on their 2017 boat.

Eliminating the model year solves the problem for the manufacturer and dealer but can be confusing for buyers. Other outboard manufacturers, including Mercury and Honda, adopted Yamaha's practice, and most outboard engines today don't have model-year designations. Outboard manufacturers say that until they make a significant change to an engine, the year it was built is irrelevant. While that's true, buyers are concerned that if there's no model-year designation, they don't know if they're getting the newest technology.

Fortunately, there's still a way to determine when an outboard was built. After discontinuing model years, engine manufacturers replaced the model-year designator on the engine's serial number with a code that signifies an "era" in which all engines are supposed to be the same, with similar upgrades. Consumers, however, are concerned that with computer controls, mechanically identical engines could have electronic updates applied to a batch of similar models, and earlier ones might not benefit.

What's considered an upgrade? In the end, the engine manufacturer gets to decide what it is and when there's enough of one to create a new model. Fortunately, dealers usually know which engines in their stock have the most current changes, and you should ask before buying.

What About Warranties?

Manufacturers say that the warranty begins when the engine is sold, regardless of its build date. BoatUS members have asked BoatUS Consumer Protection about engines that may have been sitting around for two or three years. What if they've been damaged over time? By unknowingly buying an engine that may be one, two, or even three years older than their new boat, will they be hit with higher depreciation when it comes time to sell their boat?

Fortunately, the manufacturer's warranty will cover even older engines of the same model, but buyers should verify how many hours are on an engine before buying it. Manufacturers say that depreciation should not be an issue on two identical engines of the same model, regardless of age, but most buyers want the newest one available, and an older engine, even if it's indistinguishable from a newer one, is typically worth less to a first or second buyer.

The good news for consumers is that while outboard engines may not have model years, it's possible to find out when the engine was made. In recent years, a permanent sticker typically can be found on the transom bracket, usually near the serial-number sticker, that gives the month and year of engine manufacture. As a buyer, you can negotiate for the newest engine — or for a discounted older one — if you know what to look for.

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Charles Fort

Contributing Editor, BoatUS Magazine

Charles Fort is BoatUS Magazine's West Coast Editor. He often writes local news items for BoatUS Magazine's Waypoints column and contributes to Reports, in-depth tech features in every issue written to help readers avoid accidental damage to their boats. He is a member of the National Association of Marine Surveyors, he's on ABYC tech committees, and has a 100-ton U.S. Coast Guard license. He lives in California.