Bertram 31

By Jack Hornor

Revised by BoatUS editors in October 2012

Bertram 31
Principal Dimensions & Specifications
Measurements should be considered approximate and the manufacturer&s specifications may be relied upon. Bow & stern appendages are generally excluded.
Length Overall30’ 7"
Maximum Beam11’ 2"
Maximum Draft3’ 1"
Displacement/Weight10,600 lbs
Fuel Capacity170-220 Gallons
Water Capacity18-60 Gallons
Top Speed Range23-32 Knots

In 1960, Miami sailor, powerboat racer and yacht broker Dick Bertram entered the 165-mile Miami-Nassau offshore powerboat race with an innovative Ray Hunt design called Moppie. In eight-foot seas and 30-knot winds, Bertram blew the competition away and won the race in record time, two and a half hours ahead of the next boat to finish. Bertram became convinced Hunt's prototype represented the design of the future. He made a mold of the hull and in 1961 launched Bertram Yachts with the introduction of the Bertram 31 Sport Fisherman. After over 1,800 hulls, regular production of the Bertram 31 ended with the 1983 model year.

In 1986 Bertram produced 23 "Silver Anniversary" versions of the 31's although none have been built since.

The Bertram 31 was a radical departure from mainstream thinking about what made a powerboat perform well in a variety of conditions. The most unique feature of the Bertram 31 is what has become know as the deep-vee hull form. Typically planing hull powerboats had fairly steep deadrise (the angle of slope from the hull centerline to the chine) in the forward sections that gradually flattened to about a five to ten degree angle at the transom. Designers felt if the deadrise were further increased in the after sections a significant increase in horsepower would be needed to raise the boat onto and maintain a plane.

Hunt reasoned that by incorporating lifting strakes along the bottom he could provide adequate lift without requiring excessive horsepower and, at the same time, significantly improve performance and ride. The Bertram 31 and its prototype were designed with a remarkable 23-degree angle of deadrise at the transom. There were three lifting strakes on each side from the keel to the chine. The concept worked and Hunt's deep-vee hull has remained the standard for performance-oriented, mono-hulled boats for more than 40 years.

The 31 actually measures 30' 7" length over all, has a beam of 11' 2", a draft of 3' 1" and displacement of around 11,000 lbs.

It may sound trite but they just don't build them like this anymore. In my opinion, the Bertram 31 is one of the most robustly built boats of any size or material. This likely explains why many people are so willing to spend many thousands of dollars to renovate and repower older models. Hulls are constructed using fiberglass cloth, woven roving and fiberglass mat in combination with plastic resin. Lay up is more than 1/2" thick on the bottom near the centerline and, even at the sheer, measures in excess of 3/8". Decks are also a solid laminate of fiberglass and resin and measure 1/4" thick or greater in most areas. The deck and hull are joined on a narrow outward flange with mechanical fasteners every 4". There is very little use of core materials. Where core is used it is in combination with substantial fiberglass coverings.

Because the design of the 31 includes tumblehome (narrowing of the hull at the sheer) towards the transom and a molded-in spray rail at the chine, boats had to be built in split molds that could be separated after the hull set. The additional finish work on the parting line of the mold added to the cost of production and likely helped lead to Bertram's decision to discontinue this model. The Bertram 31 is one of only a few production boats I have come across in my career that I can say I have never seen any significant structural failure, even on boats that have endured very tough service.

Realizing early on that demand could be rather limited for a spartan 31' fishing boat, Bertram soon expanded its line to include a variety of models built on the same proven hull form. For the most part, differences in models were very subtle. The Flybridge Cruiser is nearly identical in profile appearance to the Flybridge Sport Fisherman although the cabin area is closed off with a bulkhead and door at the after end of the hardtop. The Express and Bahia Mar models are slightly different in appearance in that they have open helm positions and no fly bridges.

Many 31's have been highly customized over the years with the addition of towers and custom fly bridges but there is no mistaking the distinctive Bertram 31 sheer line and hull form.

Make no mistake; the Bertram 31 is first and foremost a fishing boat. In fact, this is one of a few small boats that can still be regularly found competing in bluewater fishing tournaments. This does not mean the 31 can't be an efficient, although somewhat spartan, family cruiser. All models were equipped with V-berth accommodations, a marine toilet and minimal galley facilities. The Cruiser and Sport Fisherman models were equipped with a dinette area that could be converted to a "cozy" double berth. The cockpit, however, is where this boat shines. There is more than a 110 square feet of space, which accounts for more than half the space aboard. There is plenty of room for a fighting chair with room left over to get around.

Most Bertram 31s were powered by two 330 horsepower Mercury Marine inboard engines. The combination provides a respectable cruising speed of about 26 miles per hour and top speed of around 37 miles per hour. Over the years several models of General Motors, Caterpillar and Cummins diesel engines were offered as optional power. The diesel engines generally resulted in slightly less speed but improved cruising range. The engines are located in near midship in insulated raised boxes. Engine boxes are completely removable allowing excellent access for service to all parts of the machinery. Fuel capacity of the original Bertram 31 was 170 gallons and was increased to 222 gallons with the 1972 model.

The Bertram 31 has become legendary for her ability to handle big seas in relative comfort and safety. But another attribute that is absolutely necessary for a successful fishing boat is maneuverability. The 31 is easily controlled whether in head seas, following seas, fighting a fish or docking at a marina, yet another reason for her loyal following. As is the case with most boats, the Bertram 31 is not without her little quirks and imperfections. The ride can be and often is a wet one. The freeboard forward measures only about 44" and although there is a molded spray rail at the chine, there is little flare at the bow and powering into even a moderate chop of several feet can result in a wet ride. And, with all its advantages, there are some disadvantages to the deep-vee hull form. One is that the form provides little buoyancy at the chines. Because of this, the 31 tends to roll from side to side considerably in a beam sea particularly at slow speeds or drifting, a condition that can be somewhat disconcerting to some people.

As testament to the enduring popularity and lasting value of the Bertram 31 Sport Fisherman, which cost just under $20,000 when it was introduced in 1961, the current BUC value guide lists the value of a 1961 Sport Fisherman between $33,700 and $37,500. In fact, a substantially restored and repowered early 60s Bertram could sell for considerably higher than the BUC value range.

Searching the Internet recently I was able to find five Bertram 31s currently offered for sale ranging in price from $35,000 for a 1968 gas powered model to $149,000 for a 1976 gas powered model. Worton Creek Marina in Chestertown, MD recently purchased three 1970s vintage 31s that had been used by the State of Virginia marine police. Plans call for totally remanufacturing the boats with brand new Cummins Diesel engines and everything upgraded to current standards from wiring to seat cushions. The base price of the remanufactured boats is expected to be $150,000. Burr Yacht Sales in Edgewater, MD, who was a long time Bertram dealer and continues to specialize in used Bertram models, is also a good source.

There is an active Bertram Owner's Club with nearly 1,000 members nationwide which publishes a newsletter and helps members to locate hard-to-find parts and repair manuals. For further information you may contact Bertram Owner's Club, P.O. Box 2324, Seal Beach, CA 90740.

Some have argued the Bertram 31 is the best powerboat ever built. I would argue that the matter is much too subjective to ever pick one best boat but the Bertram 31 surely ranks near the top of my list for this size and class. If there were a hall of fame for powerboats there is no doubt this would be one of the very first inductees.

Naval architect Jack Hornor was the principal surveyor and designer for Marine Survey & Design, Co., based in Annapolis, MD. He was on the boards of the American Boat and Yacht Council, the National Association of Marine Surveyors, and the Society of Boat and Yacht Designers. He and his wife sailed their Catalina 42, Legacy, based on Maryland's Eastern Shore.

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