Once An Innovator, The Bertram 31 Is Now A Classic

In 1960, Miami sailor, powerboat racer and yacht broker Dick Bertram entered the 165-mile Miami-to-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 more than 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, with oak interiors and custom hull striping, but 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. It's most unique feature is what has become known 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 5- to 10-degree angle at the transom. Designers felt that 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, monohull boats for more than 40 years.

The 31 actually measures 30 feet, 7 inches in length over all; has a beam of 11 feet, 2 inches; a draft of 3 feet, 1 inch; and a displacement of about 11,000 pounds.

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. Layup is more than ½-inch thick on the bottom near the centerline, and even at the sheer, it measures in excess of 3/8 of an inch.

Decks are also a solid laminate of fiberglass and resin and measure ¼-inch thick or greater in most areas. The deck and hull are joined on a narrow outward flange with mechanical fasteners every 4 inches. 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, these 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 never had any significant structural failure, even on boats that endured very tough service.

As these vintage photos show, the Bertram 31 has been around awhile. Beginning in 1961, more than 1,800 hulls were built.

Realizing early on that demand could be rather limited for a spartan 31-foot 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 31s 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, it 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.

Original equipment for all models includes V-berth accommodations, a marine toilet and minimal galley facilities. The Cruiser and Sport Fisherman models have a dinette area that can be converted to a "cozy" double berth. The cockpit, however, is where this boat shines. There is more than 110 square feet of space, which accounts for more than half the space aboard, and there is plenty of room for a fighting chair, with room left over to get around.

Most Bertram 31s were originally powered by two 330 horsepower Mercury Marine inboard engines, a combination that provided 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 yielded slightly less speed but improved cruising range.

The engines are located 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 inches. 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 despite the advantages associated with the 31's deep-vee hull form, there are some disadvantages, too. 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 market value for a 1961 model actually exceeds what the boat cost when new. In fact, a substantially restored and repowered early 60s Bertram could sell for considerably more.

There is an active Bertram 31 Owner's Club with nearly 1,000 members nationwide. It publishes a newsletter and helps members 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 or Fax (562) 598-8715.

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.

Jack Hornor, NA is the principal surveyor and senior designer for the Annapolis-based Marine Survey & Design Co. Hornor writes for BoatU.S. Magazine and other marine publications.

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