- Devoted to the Bertram 31 boats around the world!

Bertram 31 Specifications

Nothing in power boating has equaled the continued world wide popularity of the Bertram 31. One of several Bertram 31 models, more than 1,000 Flybridge Cruisers were built over the years. While they have been out of production for many years, used models are continually in demand regardless of age or condition.

Unquestionably, the chief attribute of any Bertram 31 is her legendary deep-V bull design. In addition to her superb sea keeping characteristics (and a well-known wet ride), the 31 FBC has a large fishing cockpit and comfortable (if Spartan) cabin accommodations with berths for four.

Regular production ended in 1983, but 23 "Silver Anniversary" models were built in 1986 with oak interiors and custom hull stripping. Twin 330-hp Mercruiser gas engines powered the majority of the Bertram 31s with several GM, Cat, or Cummins diesels offered as options. The Mercs would cruise around 23 knots with a top speed of 32+ knots. Earlier diesel-powered Bertram 31s had less speed and horsepower but greatly improved range. (The fuel capacity increased in 1972 from 170 to 222 gallons.)

Over 500 changes were made to the Bertram 31 over the years; mostly cosmetic or hardware related. Note that the 31 Sportfish is visually the same boat without the cabin bulkhead and the Sedan is the same as the Sportfish without the flybridge.

Other models include the Express Cruiser, the Bahia Mar, & the Convertible or "Moppie".

Current trends are toward modern diesel conversions with the 4 and 6 cylinder inline Cummins and Yanmar being the most popular power plants. Fully restored or customized, diesel B31s can be valued as high as $175,000 & several have sold for over $200,000.

The Bertram 31 has six distinct variations:

  • FBC - Fly Bridge Cruiser, Cabin w/bridge & aft cabin bulkhead
    FBC - Fly Bridge Cruiser Layout
    "Christina" owned by Giambattista Tarditi, SESTRI LEVANTE, Genua Italy

  • SF - SportFish, Cabin w/bridge, no aft cabin bulkhead, lower controls incl..
    SF - SportFish Layout
    Tommy Drake's "Island Girl"
    Tommy Drake's "Island Girl"

  • Bahia Mar - Small trunk cabin, slightly elevated helm, small windscreen
    Bahia Mar Layout
    "Sea Horse" owned by Lee Irvin, Coconut Grove, FL

  • Express - Full cabin, raised helm amidship with large operable windscreen
    "Viscaya" owned by Capt Peter Fallon, Lake Worth FL

  • Moppie - Totally open, forward windscreen & helm
    Moppie - Totally open, forward windscreen &  helm
    Moppie - Totally open, forward windscreen &  helm

  • Sedan - Sportfish type open cabin, inside controls, no bridge
    "Silver Bay" - Owned by Art Sutch and Peter Metcalfe, Juneau, Alaska, USA
    "Silver Bay" - Owned by Art Sutch and Peter Metcalfe, Juneau, Alaska, USA

    The general specifications for the Bertram 31 are:
    L.O.A. ..............30' 7"
    Beam ...............11' 2"
    Draft.................. 3' 1"
    Fuel....................175 gal until 1968.
         In 1968 fuel was increased to 222 gal
    Power was originally gasoline and many Bertram 31's are still powered this way. Several diesel engines are adaptable and in use, including: Yanmar, Cummins, Detroit, Man, and Perkins.

    Speed varies greatly with which power plants are used and ranges from a cruise of 18 - 30+ knts. The biggest drawback of the Bertram 31 design is that it is a wet and wild ride in a head sea. This fault is generally accepted and overlooked by 31 enthusiasts who know that other positive features out weigh the negative.

    Perhaps the best features of the 31 are it's low center of gravity, large cockpit, deep-v hull, and hard chine, all of which make this boat one of the best fishing platforms on the water today. It is obvious that the 31 is designed essentially as a fishing boat and creature comforts were considered as secondary considerations. The 31 also makes an excellent dive boat.

    January 1999 issue of Chesapeake Bay Magazine reads 1800 hulls were made up to 1983 and an additional 23 were made in 1986. That puts it at 1823 total. (Thanks Joe!)
    Art Schuessler adds:  " My 31 is a 1980 f/b cruiser hull #1833 and had original 504 Cummins .I have read about 2000 were made which would seem about right since they produced them 3 years after mine was built. "  (Thanks, Art!)

    There have been many owner modifications and customizations of the 31. While most are within the original design specifications, common modifications include: addition of a generator, transom livewell / fishbox, diesel conversion, air conditioning systems, freshwater heads, etc. Some have been totally customized to the point that only the basic hull, house, and flybridge design remain original.

    From time to time, several members have wanted to build a trailer for the B31 hull. I will not get into the design of the trailer, but this link will carry you to a set of diagrams containing the Cardinal Dimensions needed to proceed...

    Cardinal Trailer Dimensions for the Bertram 31 Hull

    The Factory Cradle Diagram for the B31, (PDF format 114K)

    For those of you interested in the Original B31 Owners Manual, here it is in PDF format, thanks to Alex Moore. (64 pages & 1.3 megs)

    Here's a 1972 Bertram Brochure also in PDF Format, thanks to Joe Hlatky. (11 pages & 8.9 megs)

    You will need the Adobe Acrobat Reader installed to open the file. Don't have it? Get it here...    

    Performance specifications Submitted by Paul Gozewski (Capy) - "Slip is the first measure of vessel performance. Lower % slip is more efficient. " (More...)

    I will endeavor to bring as many examples of the 31 onboard as possible. If you would like your 31 to be included in our collection, please contact us at:


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