Bertram 31 History, Versions and Used Buying Guide

From Moppie to the most famous 31 footer ever built

During the 1958 America's Cup trials off Newport, yachtsman Dick Bertram watched a 23-foot deep-V test boat from designer C. Raymond Hunt run through rough water far better than anything around it. Hunt then drew a 30-footer that Bertram built in wood and named Moppie, his wife's nickname. In the 1960 Miami to Nassau race, a notoriously rough offshore event, Moppie crushed the fleet and set a record, and the deep-V hull's future was settled.

The original 31-footer served as the plug for a fiberglass production boat, and Bertram began building it in Miami in 1961. As Bertram later put it, so many yachtsmen were waving checkbooks at him that he had to go into business. By 1971 the company had built 1,000 boats, and the Bertram 31 ran in five versions until regular production ended in 1983. Soundings puts regular production at 1,860 boats, and 23 Silver Anniversary boats followed in 1986.

Hunt never patented the deep-V, because a small sailing magazine had published his concept before his application. That is why almost every offshore fishing hull built since owes something to the bertram 31, and why the original still has a cult following more than six decades later.

Why 24 degrees of deadrise still matters

The 31 carries 24 degrees of transom deadrise, a sharp entry and longitudinal lifting strakes, on a solid fiberglass bottom. The result is a hull that keeps its speed into a head sea and lands softly, which is exactly what you want running an inlet at dawn or punching back from the Gulf Stream in a building afternoon breeze.

The trade-off is roll at rest. A deep-V with an 11-foot beam is tender when drifting or trolling slowly in a beam sea, and some owners fit a small gyrostabilizer while others simply learn to set the spread on a quartering course. The boat also needs power and trim to stay level at low planing speeds.

Racing proved the hull. Englishman Tommy Sopwith bought a racing 31 called Thunderstreak from Dick Bertram for the 1963 Cowes to Torquay race. Restored decades later and repowered with 435 hp MerCruiser V8s, after Ray Hunt Design confirmed that a hull originally built to race at about 26 knots could take the power, the same boat won historic-class races in England at more than 50 knots, a remarkable demonstration of how much the 1960s bottom can handle.

Five versions of the 31 and which one to buy

Bertram built the 31 as a Sport Fisherman, Bahia Mar, Flybridge Cruiser, Express Cruiser and Hardtop Cruiser. Every version shares the same hull. The differences are in the deck, cabin and helm arrangement, and they decide whether a given boat is a fishing tool or a family weekender. Every version has a forward cabin with a double berth.

Every version except the Bahia Mar has a 110 square foot cockpit. The Bahia Mar was Bertram's lower-priced, open-helm 31, with a smaller cabin sleeping two, a galley and an enclosed head, and a 147 square foot cockpit that leaves room for a crew of four to work fish. The Sport Fisherman adds a flybridge over a lower station, plus a dinette that converts to a double for four berths in all, and it is the classic look most people picture when they hear 31 Bertram.

• Bahia Mar: open helm, cabin for two and a 147 sq ft cockpit
• Sport Fisherman: flybridge and lower station, sleeps four, 110 sq ft cockpit
• Flybridge Cruiser: enclosed cabin amenities under a flybridge
• Express Cruiser: single-level helm, cruising oriented
• Hardtop Cruiser: covered helm for weather protection

Rigging a 31 for offshore fishing and tournaments

Bertram sold the 31 with a basic fishing cockpit, and owners have rigged them every way imaginable since. On the classic fishing versions the engines sit under boxes in the cockpit, which double as seats, rigging stations and bait-cutting boards. Typical upgrades include an aerated transom or in-deck livewell, flush rod holders in the covering boards, a rocket launcher on the hardtop, outriggers and a tuna tower with an upper station. Bahia Mar boats often get a leaning post and a center console style layout that turns them into excellent kite and live-bait sailfish boats.

In tournament use a well-rigged 31 is still competitive in kingfish, dolphin, sailfish and inshore-offshore events where the run is under 40 miles and the crew is two to four. It will not match a modern center console on speed, but it rides better in rough water and the cabin gives shelter for an overnight or a rain squall. In Florida, the Carolinas and the Northeast you will still see 31s fishing the same inlets they fished in the 1970s.

The cockpit is low enough to wire and gaff fish easily, and the deep-V tracks well while backing down on a fish, although a 31 with original gas engines needs a careful hand on the throttles to avoid taking water over a low transom.

Diesel repowers and 31 Bertram outboard conversions

Bertram's 1972 brochure lists twin 225 hp Chrysler gasoline V8s as standard, with 300 hp Chryslers, 325 hp MerCruisers, 140 hp GM diesels or 170 hp Cummins diesels as options, and quotes top speeds of 34 to 37 mph (about 30 to 32 knots) for the gas Sport Fisherman. Diesel repowers are the most common modern upgrade. Mastry Engine Center in St. Petersburg has repowered more than 30 of them, and a 1981 boat tested by BoatTEST with twin 315 hp Yanmar 6LPA-STP2 diesels made 25.6 knots at 3,000 rpm on 16.7 gallons per hour, about 1.5 nautical miles per gallon, and 32.5 knots at wide open throttle (3,911 rpm) on 29.4 gallons per hour.

The other route, and a hot search topic, is the bertram 31 with outboards. Shops remove the inboards and shafts, rebuild the transom, and hang twin or triple outboards on a bracket. The gain is a cockpit without engine boxes, much lighter power, and modern reliability and speed. The risks are weight distribution changes on a hull designed for inboards, the engineering quality of the bracket and transom work, and a bill that can exceed the value of the hull. Ask for the builder's drawings and laminate schedule before you buy any converted boat.

Either way, a properly repowered 31 is typically worth more than an original gas boat, and the diesel boats appeal most to buyers who want range and lower fuel costs.

What the Bertram 31 interior really offers

Nobody buys a 31 for its interior. Every version has a forward cabin with a double berth, and the factory specification for the Sport Fisherman included a galley with sink and icebox, a dinette that converts to a second double berth and a marine toilet, for four berths in all. The Bahia Mar sleeps two but still has a galley and an enclosed stand-up head. Headroom is about 6 feet 2 inches according to Bertram's brochure, and on a hot day the cabin is a place to stow gear and get out of the sun rather than a place to live.

Restored boats often get new cushions, teak or synthetic teak trim, LED lighting, a small air conditioner on shore power and modern electronics. Keep it simple, because every pound added forward changes how the deep-V trims at speed.

Shopping the Bertram 31 for sale market

When Yachting surveyed the market a few years ago, more than 30 Bertram 31s were listed at prices from $25,000 to about $209,000, and that spread is still the story in 2026. The cheapest boats are projects; the expensive ones are restorations where someone else already paid for the hard work. Running costs are modest, roughly $12,000 to $30,000 a year for insurance, a slip or rack space, fuel and maintenance on a sound boat.

Treat any 31 as a 40 to 60 year old boat first and a legend second. A survey should concentrate on the structure, the fuel system and the engines, and a buyer should assume wiring and hoses need replacing unless there are receipts showing otherwise. Original boats carried 170 gallons of fuel in fiberglass tanks and 18 gallons of water, so ask what tankage a repowered boat has now.