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Disclaimer:   I am not a spokesperson for the US Coast Guard or ABYC. For an official interpretation of regulations or standards you must contact the US Coast Guard or other organization referenced..   More.....


Topics of interest to boat builders, repairers and owners. Subjects discussed by boating groups and forums.

On this page are issues that cause a lot of discussion pro and con in the boating community. These are my opinions. As with most things, there are two sides to every issue. I hope that these will give you food for thought and maybe contribute to a better understanding of the issues involved.

I will also post links to other online discussions or information on the subject. These will be included in the article or immediately below the article.

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For the First Time; 2 Articles,  HIN 101, and Repowering

HIN 101 For Boat Owners – Rev. 2

Disclaimer: I am not a spokesperson for the US Coast Guard or ABYC. For an official interpretation of regulations or standards you must contact the US Coast Guard or other organization referenced.   More..... 

Every recreational boat manufactured, imported, or built in the USA, and Canada, and many other countries, must have a Hull Identification Number (HIN). This is a unique number identifying each boat, in much the same way that every automobile has a Vehicle Identification Number (VIN).  The US and Canadian rules for HINs are the same and the European Economic Community (EU) has adopted very similar rules.  But some boat owners get confused about HINs, especially on older boats that weren’t required to have them, home built boats, and imported boats.


In 1972 the Federal Boat Safety Act became law, and to implement it the U. S. Coast Guard was required to propose regulations for the safe construction of boats.  As a way to determine if a boat was in compliance with the new regulations,  a HIN was required on each boat. The HIN identifies the manufacturer and when the boat was made. It is a twelve digit number.  The first three letters (in some older MICs there may be a number) are the Manufacturer Identification Code (MIC) and the last four numbers show the date of certification.  You can look up a MIC here.


The date of certification is the date the manufacturer certifies that the boat meets all the regulations that the particular boat has to meet.  But this kind of legal jargon is confusing to most people, so the last four digits, to most people, indicate when the boat was built.  Look here for the US Coast Guard version of HIN 101.

 The regulations were intended to apply to boat builders and manufacturers, not boat owners.  But boat owners became involved because all the states include the HIN in their registration process and require a HIN on every boat, even old, home made, and imported boats.    The regulations have changed and now require states to assign HINs to all boats that do not have a valid HIN.  Prior to this the state could chose to not assign an HIN to old boats. States are now also required to verify that HINs on imported boats are valid.

 Each state is assigned its own MIC to use when assigning a HIN. State MICs all start with the state abbreviation, such as NY, NJ, WN, FL,  and end in Z.  The abbreviations used are not the US Postal Service abbreviations. They are the abbreviations used for boat registrations, established in 1958. For example, a boat given a HIN by Washington would start with WNZ. 

Complicating the issue, the HIN has become a tool for law enforcement agencies to detect stolen boats, insurance fraud and other crimes.  Insurance companies also use the HIN to identify specific boats.  So it is important for all boats, old and new alike, to have a HIN. 

 Normally, a number is assigned by the builder or manufacturer. They keep a list of who the boats were sold to, by HIN.  This is an effective tool for defect recalls, and for law enforcement checking bogus HINs.

 So where does the boat owner come in?  This is not normally an issue with a brand new boat.  Most boats come with the HIN on the transom, or at or near the stern on boats with no transom.

A HIN looks like this:


So, what does it all mean? ABC is the MIC.

The next five characters are anything the builder wants to assign. It can be 12345, or 00001, or 0000A, or 32001. Whatever they want to put in there except: O, I or Q. These characters look too much like zeros or ones. Some manufacturers use a sort of code in this area. For instance, if they build a thirty footer and this is the first one then they would use 30001. Others just assign consecutive numbers, 00001, 00002, 00003, etc.

The ninth character identifies the month when the boat was certified (or built) as shown in the chart below. So if it's built in May the ninth character would be an E.

It works like this:

A: January

G: July

B: February

H: August

C: March

I: September
(yes it's an I, but it's ok)

D: April

J: October

E: May

K: November

F: June

L: December




The tenth character is the last digit of the year when the boat was certified (or built). For example, if the year is 1997 then the tenth character would be a 7, or if it is the year 2009, it would be a nine.

The date of certification is the date the manufacturer certifies that the boat meets all the regulations that the particular boat has to meet. What this means is: a manufacturer is required to certify, by placing a label on the boat, that it complies with all the regulations that apply to that boat.  The label says:

This boat complies with US Coast Guard Safety Standards in effect on the date of certification

This label is usually on the capacity label, for boats that have one, or at or near the helm station as a separate label for boats not required to have a capacity label. The date of certification can be anytime between when the boat was begun until the date it leaves the place of build.  The law says the date of certification, and also the HIN, must be on the boat before it is sold, offered for sale or entered into interstate commerce. 

So what does this have to do with model year?  Since the ninth and tenth characters are the date of certification, the model year has to agree with that date.

The last two characters are the model year. In the USA the model year is defined in the Code of Federal regulations;   Effective model year 2019

"On February 8, 2016 Congress included a provision within the Coast Guard Authorization Act of 2015 that moved the start of the recreational boat model year from August 1st to June 1st , extending through July 31st of the following year. This change allows for a 14-month model year window for recreational boats, and the definition of model year can now be found in Title 46 U.S. Code, Chapter 4302. "  USCG Boating Safety Circular #91 Dated Fall 2018

46 U.S. Code § 4302 - Regulations

Under this section, a model year for recreational vessels and associated equipment shall, except as provided in paragraph (2)—

(A) begin on June 1 of a year and end on July 31 of the following year; and

(B) be designated by the year in which it ends.

(2) Upon the request of a recreational vessel manufacturer to which this chapter applies, the Secretary may alter a model year for a model of recreational vessel of the manufacturer and associated equipment, by no more than 6 months from the model year described in paragraph (1).

Prior to this model year was defined as:

33 CFR 181.3 Model year means the period beginning August 1 of any year and ending on July 31 of the following year. Each Model year is designated by the year in which it ends.

For a time, the U. S.  Coast Guard was not strictly enforcing the month portion of the definition of the model year. A builder could begin a model year in the month they wanted but it still could not differ from the year it was built. Most manufacturers started their model year in August, but some used June or July. One even started in May.  So for instance, a boat that was built between June, 1989 and May 31, 1990, would have been labeled a 1990 model.  But their model year began on June 1 and ended on May 31 of the next year.  The USCG always enforced the year portion of the model year definition.  That is the model year on the HIN must fall within the year the model year ends.  Each Model year is designated by the year in which it ends.”

In 2009 the USCG ruled that the model year would be enforced as written. The model year must begin and end in accordance with the regulation.  If the boat is a 2000 model year it shouldn’t say 1997 or if a boat is a 1997 model year it should not have a model year of 2000.  If it was built between August 1 of 2000, and July 31 of 2001, then it is a 2001 model year. Now if it is a 2020 model year the model year must start on June 1 of 2019 and end on July 31 2020.  Yes, this is a 14 month model year.  If the model year differs from the date of certification, every time someone tries to register that boat, the state will flag it for checking. The cops will come and start asking nosy questions. Also, the owner will have a difficult time insuring the boat. The insurance agent will suspect some sort of fraud if the model year is significantly different from the actual year built.

The exception is a boat that takes longer than a year to build.  Since this is really the date of certification, then the HIN does not have to be put on until the boat is finished and ready to leave the place of build.  In a large vessel this could be several years from the start of construction.  So, even though they started in 2019, if the boat was not finished until 2023, then it could be a 2022 model year or even a 2022 if it was finished after June 1, 2022. 

There have been some additions to the HIN since 1984.  A builder can add info before and after the number.  For instance, many imported boats have a country code before the number.

US - ABC12345L409

This is a boat built in the USA.  If the two letters were CA it would be Canada.  The International Standards Organization (ISO) publishes a list of country codes.  

Additionally they can put up to five characters after the HIN.

US - ABC12345L495 - H3266

See this link for what those characters mean.

It is rare to see a 17 or 19 character HIN but they do exist.  The last five characters are a description of the boat and especially useful to law enforcement in tracking stolen boats.  The International Association of Marine Investigators has been trying for years to get the last five digits adopted by the US and the EU.  However the Coast Guard has decide to no longer pursue getting the HIN regulation changed to a 17 digit number.

What if you buy an old boat made before 1972, and it doesn’t have a HIN, or it was home built?  If you bought the boat, make sure you get a valid bill of sale from the seller.  If they have previously registered the boat you should also get the old registration. In states that Title boats you should get the title transferred as well.  If you built it, you will not have any of these. The state will ask you to fill out a form to attest that either you built the boat, or that it was built prior to 1972.  They may also ask for a Manufacturer’s Statement of Origin (MSO), or a Manufacturer’s Certificate of Origin (MCO).  Old boats or home built boats simply do not have these documents.  Only new or factory built boats have them. Some states also require you to provide sales receipts for material and equipment to determine the value of the boat for tax purposes.

They may also require someone to actually look at the boat and verify it exists.  This may mean bringing the boat on a trailer to their office, or if it is a large non-trailerable boat, having a law enforcement officer come to look at the boat.

They will then assign a HIN to the boat.  You will have to put the HIN on the boat in two places.  The requirement is for the HIN to be placed on the upper right corner of the transom, or if no transom, at or near the stern on the right side below the gunwale.  A duplicate has to be put in a concealed location.  Remember where this is.  If you ever sell the boat you will need to pass this on to the next owner.

It must be “permanently affixed”.  This means put on in such a way that any efforts to remove or change it will be obvious.  It can be burned, etched, carved, or stamped.  You can put it on a plate or label as long as the plate or label cannot be removed.

Just to confuse the issue even further, before 1984 there were two ways to put the date of certification on the HIN.  It could look like this ABC000011272, or ABC00001M73E.  Both of these are valid and indicate a boat built in December 1972, (hence 12  and 72 on one, or M for model year 73 and E for the month of December).  This was very confusing so in 1984 the current HIN was adopted.

Registration rules vary from state to state, so contact the state’s Boating Law Administrator.

To make this even more muddied, imported boats are now entering the country with HINs that appear to be valid.  They look just like US or Canadian HINs and they are valid in the country of origin, but not in the USA.  All Canadian HINs are valid in the US and vice versa.  Why aren’t most foreign HINS valid?  It goes back to the MIC.  The US and Canada have a shared MIC code database.  Since 1972 they have assigned approximately 40,000 MICs.  At any one time only about 4500 are active, but companies go in and out of business daily. 

Then the ISO adopted the MIC assignment system.  The EU incorporated this in their code called the Recreational Craft Directive.  Each EU country is now assigning MICs to their boat manufacturers.  Many of these are identical to MICs assigned by the US and Canada.  So a boat with a MIC of ABC may have been made in any of several dozen countries.  In other countries that also follow the ISO rules, such as Australia and New Zealand, MICs are being assigned to identify their boat builders. There is no international database of boat manufacturers to verify a MIC of an imported boat.

The rule in the US is that the importer is supposed to get a MIC from the US Coast Guard and assign valid HINs to the boats.  Unfortunately this is rarely done and there are thousands of imported boats sold each year in the US with invalid HINs.  This usually becomes a problem when the boat is registered with a state.  States are now required by Federal Regulations to verify the HIN on an imported boat to determine if it is valid, especially the MIC. They have access to the US Coast Guard’s MIC database which contains both US and Canadian MICs. If the MIC doesn’t match, then the HIN is not a valid US HIN.

So, if you buy an imported boat and it has a foreign HIN (other than Canada) you may be asked a lot of questions when you try to register it or document it with the US Coast Guard.  They will run the HIN through the MIC database and the manufacturer will not be correct.  If the HIN is not valid, you should contact the importer to see if they have registered with the Coast Guard and gotten a MIC.  You may have to contact the US Coast Guard (or Canadian Coast Guard) to get it straightened out and get a valid HIN for the boat.  If you import the boat yourself, you will have to get a valid HIN.  If you are going to register it with a state they will assign a state HIN.  If documenting the boat the USCG may have to assign a valid HIN.

So, what to do if you get a boat with a bogus HIN, that is, there is a valid error in the number, or someone altered the HIN?  People have been caught altering HINs to make the boat a newer model, or to try selling a stolen boat.  The best thing to do is contact the boating authority in your state, and the US Coast Guard Office of Boating Safety 202-372-1077.  Make every attempt to get this straightened out, because if you don’t it will come back to haunt you.  Suppose you get boarded and they run the HIN?  Or, you get a safety check by local law enforcement at a boat ramp and they discover the bogus HIN,  or you try to sell the boat.  The boat may be impounded, it won’t be returned until the investigation is complete.  So, get it fixed as soon as you discover the problem.
©  newboatbuilders.com 2009  revised 04/06/2019

More Info for Boat Owners- Repowering.

Horsepower ratings and re-powering your outboard boat:

Repowering an outboard boat is a subject that gets frequent and often hot discussion on many boating forums.  Of course, if the owner simply wants to replace their current outboard with a new one of the same rating, that is not an issue.  Where it becomes an issue is when they want to put on a higher horsepower motor. The issues here are: safety, boat performance, fuel consumption, and legality.


What are the safety issues?  They are primarily stability at rest and stability when moving, and an issue of flotation.  Most small boats are required by Federal Law to have positive flotation. That is, if the boat fills up with water, it will not sink and will float upright.  The law applies to monohull outboard boats under 20 feet, but manufacturers put flotation in almost all types of boats up to about 26 feet.  One of the crucial factors in getting a boat to float upright when swamped is the weight of the outboard. There is a separate calculation for the right amount of flotation to support the engine in an upright position.  If you put a bigger heavier engine on, the boat may no longer float upright when swamped.

Another problem is stability at rest, generally called static stability. The manufacturer does calculations using the weights of all the materials on board. They try to balance the weights so that the boat floats without a list and is balanced both side to side and fore and aft. They also try to make the boat less sensitive to movement of weight, that is if you move yourself or some weight to one side, the boat doesn’t dramatically heel or suddenly roll over. Part of the calculation is the weight of the engine. With an outboard mounted on the centerline of the transom, the vertical center of gravity of the engine becomes very important. It should be only a few inches above the top of the transom. If you put a much larger engine there, the vertical center of gravity moves up, making the boat easier to heel (lean over). For a better explanation of this see Stability Of Small Boats

The weight of the engine also affects the longitudinal center of gravity, that is, the position of the center of gravity lengthwise. The heavier engine moves the CG toward the back of the boat, causing the stern to go down and the bow to go up. This affects the stability of the boat making it more sensitive to leaning or rolling over. It lowers the transom in the water making it easier for waves to wash over the transom and into the boat.

Stability of the moving boat is called dynamic stability. It is affected by the static stability, and the hull form. As a boat rises on to a plane, less of the hull is supported by the buoyancy of the hull, and more is supported by dynamic forces, but the dynamic forces work over a much smaller area of the hull than the buoyancy forces do when standing still. In addition, the vertical CG moves up as the boat rises, reducing the forces acting to keep the boat upright. So any shift in weight or motion of the boat to one side is resisted by less force than when the boat is standing still. Putting a heavier and more powerful engine on the boat changes the balance and may cause the boat to have erratic behavior such as chine walking (oscillating side to side) and porpoising (the bow oscillates up and down). If the change is extreme it may result in the boat nose diving, or suddenly flopping to one side. Also it could cause the boat to kite (fly up in the air) or swap ends (spin out). These behaviors can cause serious injuries and can be fatal.


Most of the people who put on a bigger engine do it to simply make the boat go faster. They are usually very disappointed to find that they don’t gain much, maybe 1 or 2 miles per hour. This is because the speed of a boat is a combination of the hull form, length of the boat, the width, the weight of the boat, the horsepower, and the propeller. For most outboard boats to gain 5 – 10 mph you would have to almost double the horsepower. They could have achieved the same increase in speed by cleaning up the bottom of the boat, making sure the planing surface is straight (not curved) and trying different propellers.They would have gained 1 or 2 mph and made the boat more efficient, saving gas.

Fuel Consumption:

A bigger engine will consume far more fuel than the smaller one. To gain more horsepower, and thus more speed, you have to expend more energy. That simply means more gas. To gain 5 – 10 mph you would have to almost double the horsepower, significantly increasing fuel consumption.


The Federal Regulation for horsepower ratings for monohull outboard boats under 20 feet in length (33 CFR 183 subpart D), requires a boat manufacturer to place a label on the boat specifying the maximum safe horsepower for that boat.  The horsepower rating is determined using a formula specified in the law. See my page on horsepower

This regulation does not apply to boats 20 feet and longer, and does not apply to multihulls, pontoon boats or inflatables.  But the crucial point is, this regulation applies to manufacturers, not boat owners.  So, is the boat owner violating the law if they put an outboard on their boat that exceeds the value on the label? 

Not from a Federal stand point. The Coast Guard is not going to cite you for over powering.  If the boat is erratic and obviously a danger they may cite you for negligent operation, but that is another issue.

What about state laws?  Yes! Many states have passed laws requiring that you cannot exceed the values on the capacity label, which includes the horsepower rating. So by simply putting a larger horsepower motor on your boat you may have violated state laws and could be fined.

What about boats over 20 feet?  Again, if the boat has a label with a horsepower rating, the state may cite you, even though the label is not required by Federal regulation.  State law enforcement officers look for the label. They make no distinction between a Federally required label and a label voluntarily placed on the boat by the manufacturer. So, should you remove the label?  No,   because, you may be caught in a spider web of liability issues with your insurance company and if you have an accident, with someone suing you. The same applies to other boats such as pontoon boats and inflatable boats that have a label but are not required by law to have one. Both the American Boat and Yacht Council (ABYC), the industry standards organization, and the National Marine Manufacturers Association (NMMA) require their members to put capacity labels on the boats produced by their members. That includes the manufacturers of about 80% of the boats sold in the USA.

Most boat manufacturers use the ABYC or NMMA standards as their guide.  The NMMA standards are taken directly from the ABYC standards. Most attorneys and courts use the ABYC standards as the defacto standard.  So if the manufacturer puts a label on the boat in accordance with ABYC that is what you will be held to. Marine surveyors and marine accident investigators also use ABYC standards as a guide. If during a survey or investigation they find that your boat exceeds the horsepower rating for that boat, they will note that in their report. This will not help you if you are charged or sued.

The conclusion: Don’t do it. If you want to go faster, get a bigger boat!

©  https://newboatbuilders.com 2017 All Rights reserved

Links on this page will be moved to Ike's List when the topic is changed.

Hottopics! Downloadable PDF files. This is copyrighted material.  You may download and print these for your own use, or for educational purposes, but not for commercial use.

Battery Group Number: Does Size Really Matter?

Batteries and Chargers

Grounding. Our connection to the earth.

Grounding an Outboard

Portable Generators On boats. Pro and Con?

Carbon Monoxide:

Sophias Law and Carbon Monoxide

NPR Article on; Carbon Monoxide Poisoning From Portable Generators Proves Predictable and Deadly  https://www.npr.org/2019/12/04/


Corrosion On Boats

Safe Loading and Capacity
Boat Load Capacity VS Available Seating and the Formula for Persons

How Many People Is Too Many?

Stability on Small Boats

Horsepower and repowering.

Other Subjects:
HIN 101 For Boat Owners Rev2.

Fiberglass over wood or not?

Aluminum Tanks and Boats: To Paint or Not to Paint?

Much Ado About Ethanol

Ethanol Vs Isobutanol

American Boat And Yacht Council  Boat Design Net  Wooden Boat Foundation
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