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Frequently Asked Questions about Boston Whaler Boats

The following are answers to frequently asked questions about Boston Whaler boats, and are based on the contributions of a variety of participants who contributed solid information over many years of participating in the continuousWave website:

  1. How old is my Boston Whaler boat?
  2. Where is the Hull Identification Number?
  3. Is there water in a Unibond hull?
  4. How is the wiring repaired for the Combined Sidelights lamp at the bow?
  5. How is damage to a Unibond hull repaired?
  6. Can the maximum rated horsepower be exceeded?
  7. How are loose railing anchor bases repaired?
  8. How does the engine mount to the transom?
  9. What is the standard transom hole layout?
  10. What causes wavy hull sides?
  11. What navigation lights are Needed, and how are they wired?
  12. How are brass drain tubes replaced?
  13. How are rub rails replaced?
  14. Does a Boston Whaler Unibond Hull have a bilge space?
  15. How many boats like mine were made?

Q1: How old is my Boston Whaler boat?

The age of a Whaler can be discovered in several ways. The best indicator is a Hull Identification Number, or HIN. Locating and decoding the HIN is covered below. Every Boston Whaler boat made after November of 1972 should have an easily decoded Hull Identification Number affixed to the transom. For boats made before November 1972 (13-foot and 16-17 foot hulls), a list of hull numbers and years of manufacture is available in the Reference section. With this information you should be able to deduce the year of virtually any Boston Whaler hull which has an intact HIN. The Boston Whaler Company also has excellent records of all HIN's and will be able to tell you the "born on date" of the hull, the dealer to whom it was initially sold, and what model the hull was finished as. Boston Whaler's customer service representative, Chuck Bennett, can locate this information for you, but I hesitate to encourage everyone who owns a Boston Whaler boat to call Chuck. His telephone would never stop ringing. Try figuring it out on your own; all the data you need is available here.

If the hull identification numbers have been obscured or lost, the age of a hull can still be determined with good accuracy. Because of certain changes in molded components or accessories, it is also possible to deduce the age of a Boston Whaler boat just from close inspection of various features. Unfortunately, there is no precise process for doing this; you'll have to compare your hull and its appearance to the various models described in the Reference section. Small changes in production like variations in accessory hardware (running light fittings, railings, steering wheels), changes in gel coat colors (tan, off white, gray, white) can help pinpoint the time of production. The information in the Reference section is believed to be accurate but on occasion some errors have been found in the histories presented for the hulls and models.

If you reside in a state that requires boat registration--and most do--you may be able to rely on the age shown on the title or registration. However, it is common that this information is inaccurate, particularly on older boats which have been sold a few times and in different states. The boat may have been registered as a particular year based simply on good faith testimony of a registrant that was accepted by the clerk at the registrar's office without verification.

The year of sale can be a clue to the model year, but like automobiles, the boat industry often changes model years before the calendar year. Typically boats made after the first of August are titled as models of the next calendar year. The model year transition can take place as early as June.

Most dealers order boats on speculation, and it is common to find a boat that sat at a dealership for some time before actually being sold. Thus you might find a 1983 Whaler that was built in 1982 and not sold until 1985, or some similar situation. The factory also used to mold boats on speculation, which meant a boat hull could be molded and left unfinished for some time until being built into a particular style of Boston Whaler boat to fulfill a dealer's order. Modern manufacturing processes have eliminated this practice, and all Whalers are now only built to order for sales to dealers.

Because of the factors mentioned above, the date of sale may precede the model year of the boat by one year or may follow the model year by perhaps a year or more.

Q2: Where is the Hull Identification Number?

Revised December 15, 2009

The Hull Identification Number (HIN) can in appear in three forms in the Boston Whaler boat: a stenciled serial number molded into the gel coat of the hull, a metal tag mechanically fastened to the hull, a molded-in number on the hull transom. Numbering of the hull was initially voluntary but after November 1972 became a Federal requirement.

Stenciled Number

Virtually all Boston Whaler hulls are identified during construction by molding-in a contrasting color gel coat number containing about seven alphanumeric digits and apparently applied with the aid of a stencil. We call this the "stencil serial number." This number is molded into the cockpit liner, that is, it is part of the outer gel coat layer and not merely painted on top of the gel coat. Generally this number remains very durable and visible unless covered with topcoats of paint. The location of this number varies with different models. On larger boats a common location is in the bow of the boat, usually inside of a locker on the starboard side or in the center anchor locker. On smaller boats a common spot is on the inboard side of the transom on center line in the splash well area, typically within about 3-5 inches from the top of the transom. On most hulls the stencil number is black; on older boats with blue interiors the stencil number is white.

The stenciled serial number identifies the molded assembly of the hull and liner. Prior to the required HIN (November 1972) this number was the only number associated with a boat. Initially the stenciled serial number contained just numbers. This format was used on early production models of the 13-foot and 16-foot hulls. Eventually production volume required the use of a prefix, and an alphanumeric two digit prefix was then assigned to particular models. Some anecdotal evidence suggests that the 13-foot hull began to be molded with the prefix 2A, then 2B, then 2C, and so on. The 16-foot hulls were identified with prefixes like 3A, 3B, 3C, and so on. The 15-foot hull began with the prefix 5A; the 11-foot hull with the prefix 4A.

For example, a 1976 Boston Whaler 15-Sport has a stenciled number in the center of the motor well on the inboard side of the transom "5A00321". I interpret this number like this: The "5A" refers to the 15-foot hull, the "A" indicating the first sequence in this series. The "00321" refers to this being the three-hundred-twenty-first boat to be laid up in this sequence. The 15-foot hull was first introduced in 1976, so it seems reasonable that a 1976 boat's serial number would be relatively low (321).

These stenciled numbers were applied during the molding process, prior to the addition of any hardware or other components. Subsequent assembly operations could turn the boat into various different models. For example, two consecutive hulls molded in the 16-foot molds could be turned into different boats. One might become a Montauk while the second could become a Standard.

Inspection of the hull and its forward lockers will often reveal the stenciled number, if it has not been covered by topcoats of paint. If you are refinishing a Whaler, it is a good idea to mask off and preserve the original stenciled number of the hull. If the boat has been refinished with gel coat it will be quite difficult to discover the original stencil number, if not impossible. The stencil number may have been sanded off to prepare for the top coat. If the boat has only been repainted, it is often possible to reveal the original number by careful removal of the top coats. Ironically, the worse the preparation and repainting the more likely the original number lies intact beneath.

Interpreting the stenciled hull number depends on reference to Whaler's internal records. Information on the 13-foot and 16-17 foot hulls is available up to 1972. After 1972 you can determine the age by the required HIN affixed to the transom. Other than this breakdown by year for these two early models, there is no further comprehensive listing of stencil serial numbers readily available on-line.

Metal Tag

In order to comply with regulations introduced by the Federal Boating Safety Act of 1971 (FBSA 1971), after November 1972 boat manufacturers began to affix federally required Hull Identification Numbers to each boat produced. On Boston Whaler boats this was accomplished by attachment of an embossed metal tag to the outboard face of the transom on the starboard side within two inches of the gunwale. The tag was attached by metal rivets.

The HIN was required to conform to a standard. Initially two formats were used, the STRAIGHT YEAR FORMAT or the MODEL YEAR FORMAT. The formats are described below. I include dashes in the numbers for clarity but the actual HIN's may not contain them.

STRAIGHT YEAR FORMAT prior to August 1984


  MIC = Manufacturer's ID Code   BWC=Whaler
NNNNN = 5-character production or serial number
   XX = 2-digit month of production   01=January and 12=December
   YY = 2-digit year of production 

MODEL YEAR FORMAT prior to August 1984


  MIC = Manufacturer's ID Code  BWC=Whaler
NNNNN = 5-character production or serial number    
  "M" = "M" --> an indicator of the Model Year Format
   XX = 2-digit model year
    Z = Month of Production, coded
        A = August
        B = September
        C = October
        D = November
        E = December
        F = January
        G = February
        H = March
        I = April
        J = May
        K = June
        L = July

The actual year of production is deduced by comparing the model year to the month of production. Note that the month of production is coded alphabetically, with August being the sequence. This is because the model year change over typically occurred at the end of July, and boats made in August were give the next year's model year designation. This means that in any model year format HIN, if the encoded month of production is in the range A to D (August to December), the actual production year is one year earlier than the model year indicated. This was part of the federal coding used prior to August 1984. In 1984 a new coding system (the NEW HIN format) was created, which allowed the manufacturer to indicate the month and year of production and the model year separately. See more below on that encoding.

The MIC codes for other manufacturers can be found from a Coast Guard on-line database. [I have updated the hyperlink, for about the fourth time. The URL to this information seems to change often.--jimh]

Missing Letters or Numbers on Metal Tag

The embossed metal tag has proven to be less permanent than the stenciled number, and it is subject to loss or discoloration which makes it hard to read. Portions of the number may have been pre-printed and not embossed, leading to difficulty in interpretation of the number because only the embossed portion remains legible. Typically the HIN begins with "BWC", the MIC for Boston Whaler. This may have been only printed on the aluminum tag and have faded with age. The letter "M" may also have been similarly applied and faded away. The "M" indicates the use of the Model Year Format; see above. The five-digit production serial number may consist of four embossed digits (usually numbers) and a pre-printed character (usually a letter and often in the sequence A,B,C,D, and so on). The embossed aluminum tag has been reported to have been seen located on the port side of the transom, which conflicts with the federal requirements.

Molded-In Numbers and New Format

In 1983 Federal requirements compelled manufacturers to mold-in a more permanent hull identification number, actually molding in or engraving the ID into the hull surface. This seems to be the standard practice at present. This number is located on the outboard face of the transom on the starboard side and about two inches below the gunwales. Beginning as early as January of 1984 and mandatory after August 1984, the HIN format changed to the so called NEW FORMAT, described below. Also, boats produced after August 1984 were required to incorporate a hidden HIN concealed in the boat at a covered location. At this writing no details are known of any obscured location that has been used by Boston Whaler, other than perhaps being located in a cockpit locker or obscured by being under a piece of wood trim.

NEW FORMAT as early as January 1984 and mandatory after August 1984


  MIC = Manufacturer's ID Code  BWC=Whaler  also WCG=Commercial Whaler after 7/20/01
NNNNN = 5-character production or serial no. (see below for details)     
    P = Month of production 
    Y = Year of production
   ZZ = Model Year
Month of Production (P), is coded
   A = January
   B = February
   C = March
   D = April
   E = May
   F = June
   G = July	
   H = August
   I = September
   J = October
   K = November
   L = December 
Year of Production (Y) is coded with a single digit,
the ending digit of the year, and may be one year earlier
than model year in some cases.

Characters four through eight must be a serial number
assigned by the manufacturer in letters of the English
alphabet, or Arabic numerals, or both, except the
letters I, O, and Q.

To illustrate the method of decoding a HIN, consider a c.1990 Boston Whaler boat with a HIN that reads BWC5H8nnG990. The HIN is decoded as follows:

The example HIN thus identifies a Boston Whaler boat made in July 1989 and designated as a 1990 model year boat. By consulting the HIN number prefix sequence (see untitled table linked below) specific for Boston Whaler, we can further decode the 5H8nn production sequence identifier to be indicative of a 22-foot model, either an OUTRAGE, CUDDY CABIN, REVENGE, TEMPTATION, or GUARDIAN.

It has also been observed that the HIN is preceded by the letters "US" to denote that boat was manufactured in the United States, particularly on hulls intended for export.

HIN Sequence

The sequence of characters four through eight in the HIN--the five-character production or serial number, was used by Boston Whaler in a model-specific fashion. Interpretation of the five-character production number can deduce the hull length and model. Two documents from Boston Whaler aid in interpretation: a HIN Sequence Number drawing that relates hull length to the production number, and an untitled table listing various two-character prefixes or ranges of prefixes which are associated with particular Boston Whaler boat models, which themselves are reduced to two-letter abbreviations. [Unfortunately both of these documents are currently in a rasterized form--jimh.]

Boston Whaler sometimes uses a two-letter abbreviation for model names in some of their technical drawings. Below is a listing of some of the two-letter codes and what is believed to be the model designation they convey:

AL = Alert
BB = Bass Boat
CC = Cuddy Cabin
CPD ALUM = aluminum hull commercial products
CT = Cross Tackle or Fly Fish
CQ = Conquest
DA = Dauntless
FC = Full Cabin
GB = (27-foot model) (1983 to 1998)
GL = GLS model
GTX = GTX model
IB = Inboard
IM = Impact
JC = (unclear)
MJ = (possibly RAGE 15 jet drive) (1997 to 1998)
MS = Mischief
MT = Montauk
NP = Newport
OJ = (possibly RAGE 14 with OMC jet)
OMC = (possibly RAGE 14 with OMC jet)
OR = Outrage
ORII = 17 Outrage II
OR2 = 19 Outrage II (1992 to 1995)
OS = Offshore
RE = Revenge
RJ = Rage
SK = Sakonnet
SL = Super Sport Limited
SP = Sport
SR = Striper
SS = Super Sport
ST = Standard
TD = Tender
TE = Temptation
UT = Utility
VG = Vengeance
VT = Ventura
WA = Walkaround
WB = Wide Body
WD = Whaler Drive
YAM = (possibly RAGE 14 with Yamaha jet)
YJ = (possibly RAGE 14 with OMC jet)
19OR3 = Outrage 3 (1996 to 1998)

Work Boat Hulls

Whaler hulls that were molded with stronger laminates are often marked with the letters "WB" (work boat) appended to the hull identification number. Typically commercial hulls molded prior to 7/20/01 would be identified this way. Recreational hulls could also be ordered with this option. After 7/20/01 commercial hulls likely changed to using the "WCG" identifier (Whaler Commercial and Government Group) for the Manufacturer's ID Code portion of the HIN.

To aid in identification of hulls which had been molded with stronger laminates, a dot of gel coat about 1-inch in diameter was placed on the hull sides in the approximate location where the Boston Whaler logotype decal would be applied. Typically that is about 6-inches below the rub rail and about 12-14 inches from the transom, although this may vary from model to model as proportionate to the boat's hull length.

If the boat was molded as a recreational boat with the standard desert tan gel coat but had the work boat option for heavier lay-up, the color of the dot was typically red, which matched the standard logotype decal color. If the boat was molded as a commercial grade boat, the gel coat would typically be haze gray and the logotype decals applied in black, so the dot color was changed to black presumably to match. If a commercial grade boat is ordered with a special desert tan gel coat, the dot may change back to red.

Registration Information

In some states there may be procedures in place which make registration of a boat without an intact HIN a nearly impossible process. Policies like this have been implemented to make it difficult for boat thieves to re-register stolen boats with altered or missing HINs. Should you encounter a bureaucratic stonewall when trying to register an older Whaler hull that lacks a visible HIN, you might do well to point out the fact that the size and age of your boat does not exactly make it a prime target for profit-oriented boat theft rings. If you explain that you just spent $5,000 and 1,000 hours of labor to restore a 13-foot boat, you may gain some sympathy with the registration clerk.

Q3: Is there water in a Unibond hull?

Revised July 2, 2002

Worries about entrapped water in the interior of a Boston Whaler Unibond hull are common. The construction of a Whaler is based on the UniBond technique where two relatively thin uncured laminated shells are bonded together and filled with a liquid which quickly expands into foam. The boat is left in the tightly clamped molds to cure into a single structure in which the foam is continuously bonded to the laminate shells, producing a very strong and lightweight boat. To preserve the integrity of this structure it is important that the foam remain intact and bonded to the laminate.

Ingress of water to the interior of the hull structure can cause the hull to add considerable weight. Water can also rot wooden components embedded in the hull. For these reasons there is proper concern about the condition of the interior of older Boston Whaler boats and worry if the boat holds any entrapped water.

For a long time there was a wide range of opinion on whether the foam in a Boston Whaler hull actually held water or not. Upon recent first-hand experience and dissection of a neglected Boston Whaler hull, it can be confidently reported that it is entirely possible for hulls to retain large amounts of water and become so heavy that they are nearly waterlogged. It had also been thought that perhaps a change in the chemical composition of the foam had occurred over the course of many years of manufacturing, yet detailed analysis of foam samples from a wide variety of years showed remarkable similarity. Except for slight changes in composition and use of different blowing agents, the foam has apparently always been a polyurethane closed cell foam. Tom W. Clark undertook extensive research on this and has conveyed some of those results to me privately and in the Classic Whaler forum.

Finding Evidence of Water

In order for a foam interior to retain water there must be some point of ingress. Close inspection can usually reveal potential spots where this may have occurred. This is the first step in assessing the water content of a hull. Water can enter a hull though poorly sealed holes used to mount equipment, through corroded drain tubes, or through openings in the laminate skin of the hull or cockpit caused by damage.

Special attention should be given to any equipment mounted to the boat below the water line, such as depth sounder transducers or lower engine mounting bolts. If these mounting holes are not perfectly sealed they will admit water, drawing it into the wooden backing material embedded in the hull. The take up of water into the embedded wood is a particularly bad problem, especially in fresh water, as rot will occur in the wood, reducing its strength significantly. Repair of rotten wood embedded in the transom can be very costly and time consuming.

Any fitting or fastener which mounts into the cockpit floor should also be closely inspected for proper sealing, as the cockpit is often submerged with a few inches of water, particularly in the stern and motor well areas.

Many areas of the cockpit are drained overboard by built-in drain tubes. In particular the rear cockpit sump of the boat generally has a drain whose outlet is always under water. This area should be closely inspected for corrosion and proper sealing of the fitting. In their initial installation the brass tubes were sealed with rubber gaskets held in place by the rolled edge of the tube itself. With age the rubber contracts and hardens, becoming less effective as a seal. Also, portions of the drain tube interior are always in water and thus may corrode, especially in salt water. Probe the walls of the drain tubes to verify their integrity. The outboard end of drain tubes should be inspected and re-sealed annually.

The greatest threat to hull integrity and water ingress comes from hull damage below the waterline which has not been repaired and exposes the foam interior.

The extent of damage to the laminate can be determined by examination of the color of the underlying layer. Only the gel coat layer should be considered watertight. Damage which reveals the laminate or foam may have allowed ingress of water. The gel coat layer is white or tan. The laminate layer is bluish green. The foam layer is usually white or light brown in color. Until 1994 the foam was typically white, but contact with air can cause it to turn brownish. After 1994 the foam color was more yellowish. The foam layer is easily recognized by its texture and cellular appearance, and it can be distinguished from the laminate or gel coat very readily.

Unfortunately, many boats have bottom paint which tends to obscure any hull damage. Inspect carefully the bottom of any boat for un-repaired or improperly repaired damage.

Hydrostatic pressure from water being forced into the hull through underwater areas of damage can cause de-lamination of the hull skin from the foam, contributing to further structural problems. Waviness in the hull sides is not necessarily indicative of de-lamination. Some very minor waviness appears even in Whalers just popped out of their molds, the results of minor imperfections in the molding process. Large deviations in hull sides may be caused by foam contractions. The foam is still bonded to the laminate skin and pulls it out of shape when it contracts slightly.

The best method for locating de-lamination is to use the factory's own technique: tapping with a small plastic head hammer. The report of a hammer tap will be much different over areas that have de-bonded than on sound areas.

If you suspect trapped water, the most straightforward approach for further examination is to drill a hole in the boat in the region suspected and see what comes out. Orient the boat so that gravity will cause water to drain into the area. Drill a small hole (1/4-inch diameter) and check for outflow of water. If none appears immediately, you can cover the area with a plastic bag tightly taped to the hull. Moisture that escapes will show up in the bag as condensation or droplets--or even water. A test hole can be easily repaired, another article in the Reference section provides the details. If the hole is in the transom area and enters wood backing, you may fill the hole partially with a wooden plug, topping with epoxy and then gelcoat finish.

Other approaches to determining entrapped water have been suggested. Weighing a hull is one way, but it is made complex by several problems, not the least of which is knowing exactly how much a dry hull ought to weigh. Production variability may result in a range of hull weights being associated with a perfectly normal, dry hull. There is also the problem of all the additional equipment usually installed in the boat, like the engine, the fuel, batteries, wiring, etc. And there is also the problem of actually weighing the boat with accuracy. For these reasons it is generally not a simple matter to assess hull water content by weight, unless the boat has retained excessive water.

Moisture content meters have been used by some who have access to them, but the reliability of this approach is not well known.

A novel new approach involves making electrical resistance measurements between large metal fitting on the boat which ought to be very well insulated in a "dry" hull. This technique warrants more investigation in my opinion.

Loss of structural rigidity is generally an indicator of wet or soggy foam. The Unibond hull structure is normally very rigid and strong. If a hull has soft or sagging decks or other areas, these are all indicative of problems with water intrusion.

Over the years the Whaler catalogue has ascribed many virtues to the foam, but the evidence of battered boats in the field has shown that it is possible for actual conditions to create substantial weight gains in the hull from retained water.

Removing Water

If water is found in the boat, there are several techniques for removal, including gravity, evaporation, suction, and physical removal of the foam.

The simplest approach is just to drill several holes in the area that has entrapped water, orient the boat to promote drainage by gravity, and let it sit until the water has drained. In seasonal boating areas, a long winter's rest can get a lot of water out of a boat.

If the area of ingress is large, it may allow the water to exit by the same path it entered just by evaporation. A nice stretch in a hot, dry, low-humidity climate may rid a boat of entrapped water just by evaporation. This probably works best in New Mexico and Arizona.

Enhancing both gravity and evaporation techniques by suction is another approach. A vacuum pump attached to the hull by a hose and bagging arrangement can help de-water a hull.

If the boat is in extremely poor condition it may be necessary to resort to physical removal of water saturated foam. Some owners have even gone to the extreme of removing all the interior foam and replacing it with wooden stringers glassed to the hull. Short of this approach, it is possible to remove smaller areas of foam, dry the region, and install new foam. Precise instructions and procedures for this type of repair are available in another Reference article and in an illustrated example of the technique. You will not be able to restore the Unibond construction with new foam, because the density of the foam will not be as great as the original, nor will it be in a primary bond with the hull laminates.

Q4: How is the wiring for the Combined Sidelights lamp at the bow repaired?

The wiring for powering the combined sidelight navigation lamp on pre-1972 Boston Whaler 13-foot or 16-foot hulls (and others) was embedded in the internal foam of the Uni-bond hull. Typically three 18-AWG wires were run from the center at the bow toward the transom, embedded in the gunwales on the port side, and exiting the hull on the inboard side near the stern on the port side, although in some years and models the starboard side was used. At the bow the wires exit from the hull on the topside of the foredeck under the base of the navigation lamp fixture. At the stern the wires exit the hull and are attached to a terminal block. The wiring for the navigation lamp typically makes an airborne connection from the base of the pole over to the terminal block, usually a distance of only a few inches. The electric lamps are illuminated by application of 12-VDC power to the terminals of the terminal block. From this point all wiring was external to the hull. Wiring may have been installed from a console switch to the terminal block, or an even simpler arrangement may have used a short jumper from the terminal block to a battery. Note that many early Whalers were powered by engines with pull starting and thus did not have a large lead-acid starting battery aboard. The navigation lights could be powered by a lantern battery, and the switch mechanism could have been as simple as connecting a wire from the terminal block to a post on the lantern battery.

The third wire to the bow was included as a back up in case one of the wires failed. If you are lucky, a recently failed wire may be replaced with the unused third wire, but it is often seen that all three wires fail from corrosion at about the same time.

After c.1972 Boston Whaler changed to running the wiring external to the hull for most of the path forward, using the rub rail to conceal the wires. Carefully drilled holes led the wires from the rub rail track back into the hull to the base of the lamp fixture at the bow and to the terminal block in the stern. At the bow, below the fixture there typically is a 0.5-inch diameter hole with a depth sufficient to meet a 0.25-inch hole coming from ahead which passes through the center of the rub rail track.

Replacement of the wiring inside the hull is not possible. The best alternative is to run new wiring, using the rub rail to conceal it. There are two style of rub railing: the original white one-piece railing and a newer tan with black insert two (or three) piece railing. (See the Reference article on Rub Rails for more details). New wiring is more easily installed under the newer style railing. The wiring is run between the plastic receiver track and vinyl insert. If you have the original one-piece white railing, your best alternative (as recommended by Boston Whaler customer service) for running wiring to the bow may be to attach it under the lip of the hull-deck joint using a long, continuous piece of high-quality white tape to retain the wiring to the hull. If the hull is carefully cleaned and quality tape is used (such as perhaps 3M-Scotch 33+ Electrical Tape in appropriate width) it should be possible to get good adhesion.

If the wiring has failed on a boat with the newer style rub rail and external wiring (i.e., post-1972 boat), it should be possible to replace the original wiring by removing the rub rail insert and using the old wiring to act as a pull wire to string the new cable.

When replacing wiring, use quality marine grade wire. Use of 16-AWG is suggested if there is room. It is probably easier to run individual wires as opposed to a sheathed cable. Flat paired wire (or "zip cord") can also be used. Be sure to use tinned and stranded wire. ANCOR makes suitable wire, although when purchased at a Marine Store in small quantities it is rather pricey. The convenience is worth it and the wire is of good quality.

In many Boston Whaler classic boats it has been seen that the wiring to the combined sidelights navigation lamp has failed at some point in the wiring concealed under the rub railing. The best assumption is that the insulation of the wiring dried and cracked, and at that point water was admitted to the inside of the wire. The water (especially saltwater) corrodes the copper to the point that the conductivity of the wire is broken. The wire develops an open circuit somewhere along its length. A number of people have reported this. The best solution is to replace the wiring with new, quality marine wire. The cost of a new run is not much and will give much better reliability than making splices.

The termination of the wiring at the stern varied over the years. In some cases just the terminal block was used, exposed to the elements. Later a small molded tan cover was installed to conceal the terminals and protect them from splashing.

Wiring from the terminal block to the console may be run via the rigging tunnel if the boat has one, or across the transom and forward along the gunwale for side console boats.

It seems particularly unnecessary to consult or acquire actual Boston Whaler factory wiring diagrams for wiring of the navigation lamps. The circuit is trivial. Wire one side of the lamps to the battery negative; wire the other side to a switch which is supplied with battery positive through a fuse. Please note that it is extremely important to place the electrical disconnect in the switching circuit in the positive lead. Leaving the navigation light fixtures connected to battery positive and breaking the negative lead will create the risk for much additional corrosion of the wiring and fixtures, and it will probably result in failure of the navigation lamps much sooner than otherwise. A circuit breaker can be used in place of a simple switch if desired. The original switches were typically pull switches with a flared brass knob. Similar marine switches are still available from Cole-Hersee.

In some cases a three position switch can be used, wired so that the white all-round lamp comes on alone in the middle position of the switch ("ANCHOR LIGHT") and both sidelights and all-round light are illuminated in the third position ("RUNNING LIGHTS"). This is of dubious value as it is unlikely a 13-foot or 16-foot boat would be left at anchor overnight in an area which would require use of anchor lights. (The requirement to show proper lights at night when anchored is waived in special anchorage areas, common in most harbors with boats on moorings.)

Q5: how is damage to a Unibond hull repaired?

The hull construction of a Boston Whaler differs from most all other recreational boats. Accordingly, if the hull becomes damaged, special techniques need to be used in making the repairs. The methods of repair to a Unibond hull are described in three articles:

Very useful guidance in making repairs to gel coat surfaces that have excessive cracking and crazing can be found in a presentation created by vendor TotalBoat. The presentation demonstrates the preparation and repainting of an older Boston Whaler hull that had significant defects in the gel coat finish.

Q6: Can the maximum rated horsepower be exceeded?

The short answer is "yes", but before you do, please read this separate article in the Reference section.

Q7: How are loose railing anchor bases repaired?

Based on a technique used at a Whaler Dealership, a long-time Boston Whaler owner recommends:

  1. Remove entire bow rail and do all the bad screws at once.
  2. Drill out old holes to a 0.5-inch diameter, drilling through both glass and underlying wood pad.
  3. Fill holes flush to deck level with white Marine-Tex epoxy. Allow to cure fully.
  4. Wet sand entire rail base area and re-buff gelcoat. The Marine-Tex bonds to both the glass and wood pad, and polishes up nicely, even though it will never show under the rail bases.
  5. Re-drill the filled holes for new 1/4-inch-diameter self tapping screws.

It has been reported that repaired holes are still holding perfectly three years later. WEST System epoxy also is excellent for this application. Use their high-density filler to thicken and some titanium oxide pigment to tint. A small repair kit from WEST costs about $20 and could do many holes.

Q8: How does the engine mount ot the transom?

Typically four bolts are used to mount an outboard motor to a transom. Generally, with a new engine, the manufacturer supplies the mounting hardware. The hardware is usually stainless steel machine screws of 1/2-inch diameter and threaded with the standard 1/2-13NC thread pitch. It is also seen that machine screws with finer pitch, 1/2-20NF, are used. On some engines the mounting screws may be metric fasteners of similar strength and size. When replacing hardware use mounting screws of proper size and strength. Stainless steel fasteners are highly recommended to avoid corrosion. Stainless steel threads should be protected against galling by application of a thread compound. (For more details on this problem see this article by Joe Greenslade.)

The mounting bracket of the engine typically is designed for two upper mounting bolts and two lower mounting bolts, arranged symmetrically about the engine centerline. The upper set of mounting holes is typically provided in a series of four (or five) holes spaced 3/4-inch apart. The normal practice is to use a single set of holes in the transom, and to adjust the engine's vertical position by choosing a set of one of these four (or five) mounting holes (on the engine mounting bracket) as needed to accomplish the proper engine height. Each hole thus provides 3/4-inch adjustment in height of the engine on the transom. The lower mounting holes in the engine bracket may be a corresponding matched set of four (or five) individual holes or a slot that covers the same range of adjustment.

On some engine's mounting bracket there is a single elevated lower mounting hole. This hole is often not drilled through, but rather is threaded to accept a mounting bolt entering from the transom. This type of hole is known as a "blind hole," and it is presumed the choice of a threaded hole was done avoid a protruding bolt and nut that might interfere with other parts of the engine mount in that area. Use of this hole allows the lower mounting hole in the transom to be located higher. See below why this may be desirable on certain models of Boston Whaler boat.

Prior to c.1984 there were a number of different mounting bracket hole patterns in use by various manufacturers. To create a standard, the marine industry adopted a specific layout to be used with all outboard motors. It is believed this standard was patterned after the one used at the time by OMC, the makers of Johnson and Evinrude brands, and used by OMC beginning as early as 1960 on certain models. Engines made prior to c.1984 and by makers other than OMC may have different mounting bracket hole layouts, and the transom of boats to which these engines have been installed will accordingly be drilled in different locations.

When engine mounting height is measured in units of "holes" the unit of measurement is in 0.75-inch increments, that is, the on-center spacing of the pre-fabricated holes in the engine mounting bracket of almost all engines made in the last three decades. The terms "up" and "down" refer to the position of the engine relative to the transom, not to the location of the holes relative to the top of the transom. That is, "one hole up" means the engine will be raised 0.75-inches relative to the transom.

Problems specific to Boston Whaler boats

On some models of Boston Whaler boats, the arrangement of the transom and the splash well did not provide sufficient depth to permit using the lower mounting hole position found on the standard engine mounting bracket in use after c.1984. If this hole were drilled in the standard position, it would exit the transom below the level of the splash well on the inboard end, and thus it would not be accessible. A number of solutions to this problem have been seen in existing installations on older Boston Whaler boats.

Where transom holes and engine mounting bracket holes do not align, particularly for those older boats with shallow splash wells, a recommended solution is to use an intermediary plate, commonly available as a "jack plate" or a "lift plate". These plates are not expensive, and are available in aluminum which can easily be re-drilled on the transom side with holes matching the existing layout. On the engine side the plate should fit most all engines made after c.1984 which conform to the standard hole pattern for mounting. The plate will also create a small amount of engine set back, itself possibly a desirable condition. (See the article on Engine Set Back Brackets for more information.)

On many older engines, particularly ones of less than 50-HP, it was common that the engine was fastened to the transom by clamps. In some cases the angle of the clamp bracket did not fit flush against the transom top of the Boston Whaler, and a special mounting bracket was supplied by Boston Whaler to create a small wedge on the top surface of the transom so that the engine weight could be spread across the whole surface of the top of the transom and not bear on a single point or line of contact. These were specific to each engine brand. Older Mercury engines required this bracket for proper installation on a Boston Whaler transom.

In most installations the bolts are installed with their heads on the inboard side of the transom. A large washer is used to spread the compressive load, or in some cases a metal backing plate is used. Decorative metal plates are also available, including ones engraved with "Boston Whaler" or other applicable legend. The length of the machine bolts should be such that they do not protrude excessively on the outboard side of the transom where they could lead to interference with the engine's normal operation and movement. Having the threaded portion of the bolt protrude slightly can be useful for installing sacrificial zinc or magnesium anodes to prevent corrosion. These are generally threaded 1/2-13NC. Having the finished head of the bolt installed in the splash well makes for a cleaner installation, and reduces the possibility of snagging lines, cables, feet, or hands against a protruding bolt shaft. In general, the engine manufacturer provides recommendations for installation that should be observed in preference to any other advice.

Drilling of the holes in the transom should be done with great care and precision. (See below for more advice on how to properly locate the holes.) Prior to installation of the fasteners, proper sealing must be done. One recommendation is to drill the mounting holes slightly oversize, coat the interior of the holes with epoxy to seal the wood against any moisture penetration, and then to re-drill the hole to the correct (smaller) size. This creates an epoxy barrier or annulus around the hole. Liberal use of sealant is recommended in any case. The lower mounting holes must be especially well sealed as they will likely be immersed in sea water at all times when the boat is afloat. The usual mounting bolt is 1/2-inch diameter. The recommended hole diameter is typically 17/32.

The need to prevent water from entering the wood embedded in the transom is paramount! Do not underestimate the damage this can cause.

Q9: What is the standard transom hole layout?

It is believed that the hole arrangement currently in use by most engine manufacturers follows these dimensions:

There is no point in drilling holes in the above pattern if they do not match those on your engine. Generally a hole template is supplied with a new engine. Absent that, a template could be made from the actual holes on the mounting bracket of an existing engine. Locate the holes as specified with respect to their position from the top of the transom.

On some engines, notably those from OMC, the engine mounting bracket contained a machined hole which could accept a threaded fastener, typically a 1/2-13NC screw. This is called the "blind hole." The blind holes were vertically spaced only 6-inches on-center from the upper mounting holes. The blind holes were horizontally spaced on 10 and 3/4-inch centers symmetric to the mounting bracket centerline, that is 5 and 3/8-inch from centerline. These holes were often used to mount OMC engines on Boston Whaler boats which have a shallow engine splash well.

Q10: is a wavy hull side a problem?

There are some reports of the appearance of wavy indentations in the hull sides of older Boston Whaler boats of all sizes and ages. Manifestations of waviness in the hull sides of classic Boston Whaler boats is assumed to be the result of contractions of the foam interior after the boat has been removed from the mold. As long as the bond between the laminated hull skin and the foam remains intact, these waves or dimples do not represent a structural problem. Tapping with plastic hammer and listening for a change in the sound is an effective way to test the bond between the hull skin and the foam.

This condition was particularly common in some OUTRAGE 18 hulls made in 1981 and 1982. Hulls which were severely affected were replaced under the terms of the factory warranty.

Although the waviness in the hull sides may not be a structural problem, it certainly is a cosmetic problem, particularly when the depth of the dimples is more than a quarter-inch or so. The value of the boat will be reduced because of this, particularly for a buyer who is looking for a classic Boston Whaler boat in excellent condition.

Q11: What Navigation Lights must be shown, and how are they wired?

The navigation rules themselves are the authoritative source for required vessel lighting. The rules for a power-driven vessel when underway are given in RULE 23. These rules are written in very clear and unambiguous language. Long discussions about them and personalized interpretations of how to implement them are not authoritative. Equip your vessel with the proper lighting, and display it when required. For boats less than 12-meters (and thus practically all Boston Whaler boats) there is a simplified lighting scheme which requires only sidelights and a white all-round light.

For guidance in the electrical wiring and use of specialized marine-grade switches that have been designed to make control of vessel navigation lights very simple, refer to a separate article in the REFERENCE SECTION.

Q12: How Are brass drain tubes replaced?

The repair of drain tubes is described by experts as "easy." Use a large flat blade screwdriver as a pry bar to remove the flare from the existing drain and collapse the brass tube onto itself. The tube should come easily from the drain hole passage; the OEM tubes were not caulked in place. Keep this in mind if you think about caulking a replacement in-place in the hull. After removing an old drain, check the surrounding foam interior of the hull for signs of water retention, and, if the foam is wet, allow the water to seep out and assist the foam in drying.

Boat supply centers often sell thin-walled brass tubes for use as replacement drains under the Moeller or SeaFit brand, but typically the length of these will be too short to be useful for most Boston Whaler drain replacements. The pre-formed flare on these tubes is also not rolled enough to retain an O-ring or gasket. Generic thin-wall (0.032-inch) brass tubing is available from McMaster-Carr and elsewhere. The tubes come in different lengths and diameters, so match the replacement to your original size. The following part numbers from McMaster were current as of c.2010 and c.2014:

You install the tube and pre-cut it to the proper length, allowing for enough material (0.125 to 0.25-inch) to extend beyond the hull to roll into a lip. In most locations the orientation of the existing hole to the deck or hull will not be at a perfect 90-degree angle, and a matching angle cut of the tubing will be necessary. The tubing must be cut to conform to the contour of the hull or deck.

It is strongly recommended that prior to attempting to form the end of the brass tube it be pre-heated to a moderately-hot temperature and slowly cooled to anneal it to increase its ductility; this helps to avoid splitting of the brass during the lip forming process. Practicing the lip forming operation with an inexpensive piece of generic tubing may be beneficial for first-time installers. Place the new brass tube into the drain passage and manually form the ends into a rolled lip, using either a suitable ball-peen hammer, or, if the space and configuration permits, a forming or flanging tool. When accomplishing the forming or flanging, use of an assistant to hold the tube in place is almost universally necessary. The forming tool can be adapted to work in non-90-degree situations by the use of small wedge-shaped shims and by running the threaded portion of the tool at an angle through the hole.

A rubber gasket or O-ring is used to help provide a seal at each end under the rolled lip. It is recommended that both ends also be sealed with caulk to the hull or deck to ensure a water-tight fit. Some think the O-rings are unnecessary and hinder installation; they simply caulk the ends to seal them.

If below the water line, the outboard end of the drain should be protected with a clam shell vent, located so that it covers the forward half of the drain. This creates a venturi effect when underway which improves draining and also protects the leading edge of the drain from being blasted with high-speed water. Typically a Perko clamshell vent is used, but two additional holes are drilled into its mounting flange to allow for two extra screw fasteners.

Several photographs showing the forming tool and use of the forming tool to install a drain can be seen in a recent article. Also, be certain to read Jeff's excellent narrative on drain tube replacement and view his many images. Jeff goes into much more detail and illustration than given here. If you crave more information, you can, in a long, rambling thread whose images links no longer work, find a few more details. Whether or not one can gain the necessary skills of metal forming by reading a narrative of the process is unknown. Your results may improve with repeated attempts. Remain calm during the process. Remember, it is "easy."

Q13: How Are rub rails replaced?

Please see the separate, comprehensive, illustrated article on rub rails in the REFERENCE section. It actually predates this FAQ.

Q14: Does a Boston Whaler Unibond hull have a bilge space?

A Boston Whaler boat is constructed with a double-bottom hull. A double-bottom hull has an outer hulls that is in contact with the the sea, and an inner hull which acts as a liner to the outer hull. The space between an outer hull and an inner hull in conventionally constructed boats is open and is called the bilge space. In a Boston Whaler Unibond hull this space is not open. The space between the outer hull and inner hull or liner is filled with foam as part of the construction process of creating a Unibond hull. This space is also completely sealed off, and no access is provided to this space. Thus there is no bilge space on a Unibond hull.

The exposed outer portion of the inner hull is also generally the cockpit and cabin deck. The inner hull or liner component is typically molded with intentional low spots or sumps, designed to collect water that will be on the deck. There may also be deep deck lockers or storage compartments provided in the inner hull or liner mold. All of these spaces can collect water. Typically any sump area will have a through-hull fitting to the hull bottom that will drain the area to the sea. Pumps that are electrically operated may be provided in these sump areas to lift water that has accumulated to the deck level and then to overboard outlets to the sea.

Q15: How many boats like mine were made?

Questions about the volume of production of a particular Boston Whaler model of a particular length and for a particular year are often asked, but there generally is never a good answer, unless the boat happens to be a very early production 13-footer or 16-footer. For those two boats made prior to 1972 see the 13-foot and 16-foot Reference section; listed there are are ranges of stenciled numbers by year of manufacture for those boats.

For other models I am not aware of any definitive source of information about the total production volume of any particular Boston Whaler boat.

It may be possible to draw an inference about the anticipated production volume by looking at the range of hull numbers allocated to a particular model. In the FAQ answer at Q2: Where is the Hull Identification Number, you will find information on the HIN SEQUENCE drawing of hull numbers that Boston Whaler allocated to various boat models that had federal hull identification numbers. These HIN sequence numbers appear in the federal hull identification number, so they are only useful for boats made in c.1972 and afterwards, as that is the epoch when the federal hull identification number system became mandatory for boat builders to use. The HIN sequence number is the five-character portion of the HIN that appears after the manufacturer identity code (MIC).

For example, for a 15-foot hull, Boston Whaler allocated these numbers:

1000A thru 3999A followed by
1000B thru 3999B followed by
1000C thru 3999Cfollowed by
1000E thru 3999E

The last revision of that drawing was made in 1997. On that basis the drawing only covers production from c.1972 to 1997. And it only covers boats that were given a federal HIN. Since production of the 15-foot hull began in 1976, all 15-foot classic hulls had a federal HIN. The period covered by the drawing for production of 15-foot hulls is thus 1976 to 1997, or 21-years. If 54,000 boats were made, that would have been an average production of about 2,570 15-foot boats per year.

Using the HIN SEQUENCE drawing may give you an idea about Boston Whaler's expectations for production volume for a particular hull. Note that the HIN SEQUENCE number is NOT the same as the hull stenciled number. Boston Whaler continued to identify hulls with the molded-in hull stenciled number even after they began to also identify hulls with the federal hull identification number


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