SJ23Tech Tip H08, (Updated 2026-02-26) Chuck Van de Wetering & Bob Schimmel

Index

Vintage and Revision of San Juan Sail Boats.

Three companies manufactured San Juan sailboats.  Clark Boat Company was the original in 1960, followed by Clark Boats.  I don't know the name of the last one.

DECODING HULL & SAIL NUMBERS - All vessels manufactured or imported into the USA from November 1, 1972 onward, must bear a 12 character Hull Identification Number (HIN) that uniquely identifies each vessel.  The HIN has an important safety purpose to enable a manufacturer to clearly identify a vessel that is involved in a defect notification and/or recall campaign.  The HIN is not the same as a State or province registration number, that must be displayed on the bow of a boat.  The HIN is a federal requirement in USA & Canada and a vessel registration number is a State or provincial requirement, similar to the license plate on a vehicle.  The HIN, must be shown on the state or provincial certificate of vessel registration form. 

Month of model year
AUG A FEB G
SEP B MAR H
OCT C APR I
NOV D MAY J
DEC E JUN K
JAN F JUL L

HIN FORMAT PRIOR TO August 1, 1984 - The boat manufacturer must display two identical hull identification numbers, no less than 1/4" tall, on each vessel hull.  The primary HIN must be permanently affixed to the starboard side of the transom (so that it can be seen from outside) within 2" of the top of the transom, gunwale, or hull/deck joint, whichever is lowest.  On a vessel without a transom or on a vessel where it would be impractical to label the transom, the HIN must be affixed to the starboard outboard side of the hull, within 1' of the stern and within 2" of the top of hull side, gunwale, or hull/deck joint, whichever is lowest.  The aft starboard outboard side of the hull is the preferred HIN location for many manufacturers.  On a catamaran or pontoon boat the HIN must be affixed on the aft crossbeam within one foot of the starboard hull attachment. 

Month of model year
JAN A JUL G
FEB B AUG H
MAR C SEP I
APR D OCT J
MAY E NOV K
JUN F DEC L

A VESSEL MANUFACTURED or IMPORTED AFTER August 1, 1984, has a secondary HIN affixed somewhere on an unexposed location inside the vessel or beneath a fitting or item of hardware.   In the case of Joe Fuller (listed in chart below) it was written on the bottom of the starboard cockpit seat.  You have to make a dive from the starboard settee to read it.  The purpose is to help an authority identify your vessel if a thief or vandal removed or damaged the primary HIN on the transom.  It is illegal for anyone (manufacturer, dealer, distributor, or owner) to alter or remove a HIN without the express written authorization of the Commandant, U.S. Coast Guard.  It must be on the transom if you cross a national border.  (Panache predates this requirement.  Now that I know how and where it should be located it behoves me not to write it on the wall somewhere).

The regulations prescribing the format of the manufacturer HIN are as follows:

  • The first three characters are a MIC (Manufacturer Identification Code) assigned by the Coast Guard to the manufacturer or the person importing the boat.
  • Characters four through eight are the serial number assigned by the manufacturer.
  • The last four characters indicate the month and year the boat was built and the model year.  Prior to August 1, 1984, the manufacturer had the option of expressing this in the form of a model year designation. 
     
  • An individual building a boat for their own use and not for the purpose of sale are referred to as a "backyard boat builder".  This person must obtain a 12 character HIN from their State boating agency.  The Manufacturer Identification Code at the beginning of the HIN for a "home built" boat is the abbreviation for the State followed by a "Z" which indicates that it is a State identification.

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SJ23 HULL NUMBER - The Hull Identification Number (HIN) of a San Juan 23 is imbedded on the starboard top right side of the transom.  The sail number can be ascertained from the HIN.  This same number is on the Registration Certificate or Title issued in most states.  Here is the breakdown of a hull identification for vessels manufactured after August 1, 1984: MMMhhhhhddyy. 

MMM = manufacturer ID code
hhhhh = hull serial number
dd = date of certification
yy = model year
  • For example "A4". 
  • The "4" stands for the last digit of the year of manufacture.
  • "yy" is the model year.
    *Key to Month of Model Year

This information came from the U.S. Coast Guard Auxiliary's Boating Skills and Seamanship text, 11th Edition, pages 2-2 and 2-3.

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A typical Clark Boat Company HIN cited to me as an example seems to be a modification of this and reads: CLKJO299M79A 

  • CLK would stands for Clark Boat Company, the manufacturer.

  • JO299 would identify the hull series as JO and the hull number as 299.

  • From here on I have to speculate.

  • I assume the M79A in Clark's case means it was model year 1979, certified in August.

    MONTH CODES
    A = Aug G = Feb
    B = Sept H = Mar
    C = Oct

    I = April
    D = Nov J = May
    E - Dec K = June
    F = Jan L = July

  • So if you had this HIN on your boat, your hull & sail number would be 299.

The following are HINs were given to me upon registration by several SJ23 skippers.  The year is based on the guideline above.

HULL and SAIL NUMBERS.
OWNER
 (may not be current)		 H.I.N. Mfgr ID Code HULL SERIES# HULL #

YEAR CERTIFIED

 MONTH SAIL #
Martin Murphy CLKJO009M77F CLK JO 009 M77 F = Jan 009
Ron van Amsterdam CLKJO0041M77 CLK JO 041 M77 H = Mar 041
Ted Siegel CLKJO044M77H CLK JO 044 M77 H = Mar 044
Bob Schimmel  CLKJO109M77K CLK

JO

109

 M77 K = Jun 109
Frank Toms CLKJO193M78K CLK JO 193 M78 K = Jun 193
William Best CLKJO223M78E CLK JO 223 M78 E = Dec 223
Mike Robinson CLKJO363M79? CLK JO 363 M79 ? 363
Talbert Shelton CLKJO483M80? CLK JO 483 M80 ? 483
Warren Hughes CLKJO498M80? CLK JO 495 M80 ? 495
Dave Gotchtalk CLKJO498M80? CLK JO 498 M80 ? 498
Rick Linstad CLKJO506M80H CLK JO 506 M80 H = Mar 506
Judy Trinque ? CLK JO 533 M81 ? 533
Joe Fuller CLKJO535M80K CLK JO 535 M80 K = Jun 535
Randy Cook CLKJO544M81B CLK JO 544 M81 B = Sep 544
John Woods ? CLK JO ? M81 ? 545
Paul McLemoore CLKJO656M84G CLK JO 656 M84 G = Feb 656
Bob Nolen ? CLK JO ? M85 ? 661

From the chart above it is certain that the sail number is derived from the hull number since all owners who submitted their information have sail numbers that match their hull numbers.  However, I would appreciate any clarification on this from any San Juan owner who knows.
 
SJ23 SAIL NUMBER - The hulls sold by Clark were NOT equipped with numbers on the mainsail.  Their sails were only equipped with the SJ23 logo.  It costs money to register the sail numbers and only the subsequent owners of the company registered the ones they manufactured.  The subsequent manufacturer, Clark Boats, applied both the SJ23 logo and the sail number to their mainsails.  This is yet another way of distinguishing which manufacturer built your hull, provided you still have the original mainsail!  I have no idea what the first or last serial numbers were that Clark manufactured. 

NOTE (2016):  "For many years Panache's sail number was 44 which created confusion in resolving the issue of sail numbers.  44 did not match her HIN and another SJ23 reported the same number.  Then I heard from the previous owner that 44 is actually the year in which he was born.  Really!  He needed a sail number to race the boat so his wife picked his birth year and applied the numbers to the mainsail.  Go figure! 
In 2016 I finally removed 44 from the mainsail and attached 109 to correct this long standing error.  Its amazing how a simple act in isolation (before Internet communications) can lead to such confusion later on."  I'm actually quite stoked that Panache's 109 matches JFK's PT109.  Bob Schimmel. 
 

OTHER INTERESTING TIDBITS of REVISION INFORMATION
SAN JUAN LOGO - The SJ23 logo has undergone some changes over the years with each new manufacturer, likely due to copyrights.  Note the subtle differences in font between the two logos below.

At right is the original logo from Clark.  This one belongs to hull 109, Panache.

 

 

 

At right is the logo from Clark Boats, the next generation of hulls.  I don't know which boat it belongs to.

CABIN GRAB RAILS - The grab rails on the original hulls were mounted with two wood screws driven directly into the fibreglass stubs on the deck.  This is evident from the two wood plugs at each stub a shown at left.  However, this is a new rail I made for Panache but mounted in the original screw holes. 

The grab rails on much later hulls were mounted with one machine screw into a metal plate imbedded in each fibreglass stub. Hence the single wood plug.  I have no idea at which serial number this transition was made.  If the plate is not corroded, the latter technique is definitely the stronger method.  Keep this joint well sealed, not grubby like the one on the right! 

 

 

 

 

 

 

Hatch - This design never changed, regardless of the year.  From what I can judge, it is used on all models.

Mast Base - This design never changed but the short length of track at the front of the mast became more robust in later years.


Mast Base for Racing - This deck hinge and mast foot combination was introduced for racing and is more robust than the none racing version on Panache, so I thought it good to record.  See Tech Tip F03.
 


 

 
HULL PAN - If your boat has the deck anchor locker in the bow that means it may also have the latest interior fibreglass pan.  This pan has some structural improvements over the original pan to stiffen the bow.  If you lift up the hatch under the V-berth cushion and you see a smooth-finished fibreglass compartment, you have the newer, stronger interior pan.
 
BULKHEADS - These were originally made of 1/2" thick marine plywood that has water proof glue between the laminates.  Its OK to replace a rotten one with European plywood equipped with 9 plies for more strength.  Later interiors changed the port bulkhead to half height like the starboard bulkhead.
 

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