Bertram 31

This is a deeply researched owner's companion to the Bertram 31, written by people who love these boats and respect what they can do. It is not a factory service manual, and it is not a broker's sales sheet. Before you trust a single number in these pages, do one thing first: confirm what you are actually looking at, because after six decades no two Bertram 31s are the same boat, and many are wearing engines the factory never installed.

1.1 What this book is, and what it isn't

The Bertram 31 is one of the most important powerboats ever built, and one of the most misunderstood by the people shopping for one. It is the boat that took C. Raymond Hunt's deep-v hull, proved it in the roughest running of the 1960 Miami to Nassau ocean race in the wooden prototype Moppie, and turned it into the first true production deep-V. What came out of that was a legendary rough-water sportfisherman: a roughly 30-foot-7-inch hull with steep deadrise carried from bow to transom, a boat that slices through a chop where flatter hulls slam and pound. Owners have loved these boats for sixty years, restored them lovingly, and passed them down. That is the honest good news. The honest rest of it is that the 31 is a wet boat with a full bow and little flare, its twin inboard engines are thirsty (worse on gasoline), and its balsa core decks and hull sides demand real respect and reward neglect with rot. If you want a dry, cheap, simple boat, this is not it. If you want one of the best heavy-weather 31-footers ever made and you go in with clear eyes, few boats are more worth the trouble.

This book is a companion. It is a place to understand the boat's history, its systems, its well-documented weaknesses, and the questions worth asking before you spend money. We have chased every claim to a source, and we tell you plainly where the sources disagree.

This book is not a few things, and it is worth being honest about them up front:

• It is not a factory service manual. We do not reproduce torque specs, wiring diagrams, or step-by-step overhaul procedures for your particular hull. Where a job is safety-critical, we tell you what matters and then send you to the engine manufacturer's documentation and a professional.
• It is not broker copy. Nobody paid for a word of this, and we have no boat to sell you. Where the legend outruns the facts, we say so.
• It is not a substitute for a surveyor or a mechanic. A marine surveyor who knows these boats will find things no book can, especially wet core that a moisture meter can read as falsely dry. Anything involving fuel, exhaust, through-hulls, or the DC system deserves qualified hands.

1.2 How this book is organized

Read this chapter first, all the way through. After that, the book is built to be opened wherever your question lives. There are nine chapters:

1. About This Book (this chapter): what the book is, and the one instruction that matters most.
2. History & Identity: Hunt, Dick Bertram, Moppie, the race, the production run, and the six configurations (Flybridge Cruiser, Sport Fisherman, Bahia Mar, Express, Moppie, and Sedan).
3. Factory Specifications: dimensions, weights, tankage, and the marquee numbers, with the genuine conflicts in the record (deadrise and fuel capacity among them) laid out rather than papered over.
4. Known Issues & What Surveyors Look For: the balsa core, the boxed-in fuel tank, stringers, transom, leaks, and exactly what a good surveyor checks and why.
5. Engine & Propulsion: the original twin gas engines, the classic Cummins diesel repowers, running gear on a deep-V, and how a repower changes the whole boat.
6. Systems: electrical, plumbing, steering, and the 1960s and 1970s build quirks you will meet.
7. Maintenance & Service: what these boats need, on what schedule, to stay sound.
8. Parts Cross-Reference & Sourcing: where the parts actually come from on a boat this old, including the community registry and specialist fabricators.
9. Community & Resources: the owners, forums, and writing that keep the 31 alive.

Throughout, you will see one phrase again and again: typical, verify against your vessel. We mean it literally. First uses of specialized terms are marked for the glossary so you can find them again later.

1.3 The most important idea in this book

Here it is, in plain words: this is a 40 to 60-plus-year-old boat, and every single hull is different.

Nothing else in this book matters as much as that sentence. The Bertram 31 went out of production in the early 1980s, which means the newest one afloat is over forty years old and the oldest are past sixty. In that time these boats have lived hard lives. Many were ex-charter or ex-commercial fishing boats, run day in and day out and patched to keep earning. A great many are project boats, bought cheap, torn into, and rebuilt to wildly different standards by successive owners. And most importantly for anyone reading a spec: a huge share of surviving 31s have been repowered. The factory sent most of these boats out on twin gasoline engines, but the diesel swap (the Cummins 6BT and 6BTA family is the classic one) is so common that you cannot assume anything about the engines from the year, the model, or the listing.

So the single instruction that governs the entire rest of this book is: verify everything against your actual vessel, and confirm which engines are actually installed before you rely on one word about them. Read the data plates on the engines with your own eyes. Do not trust the brochure, the survey from three owners ago, or the seller's memory. When this book says the 31 "typically" has a given tank, engine, or arrangement, we are describing the common case across the fleet, not making a promise about the boat in front of you. On a boat this age, that difference is the difference between a smart purchase and an expensive surprise. The 31 that fishes reliably every weekend and the 31 that will cost six figures to make sound can look identical at the dock and even share the same hull number lineage. Only inspection tells them apart.

1.4 A note on sourcing, and on honesty

We built this book from the best material available on a boat that never had a modern factory manual reach the public. That means we lean on three kinds of sources: the owner community, above all the registry, parts knowledge, and decades of forum threads at bertram31.com, where people who have actually cut into these boats describe what they found; the candid writing of marine surveyors, who owe the reader the truth and not the sale; and published reviews and marine journalism from the boating press. Where those sources agree, we tell you with confidence. Where they conflict, and on the 31 they genuinely do (the transom deadrise is variously cited at 22, 23, or 24 degrees, the total hulls built at roughly 1,860 or 1,986, the year the fuel tank grew at 1968, 1971, or 1972), we show you the disagreement rather than pick a favorite and hide the rest. A number you can trust is worth more than a number that sounds tidy.

1.5 A word about safety

The Bertram 31 deserves respect, and a few of its features can hurt you. Most of these boats left the factory with gasoline inboards, and gasoline fumes are heavier than air: they settle in the bilge, where a spark can cause a fire or an explosion. Many 31s predate the 1981 powered-ventilation requirement and rely on a bilge blower that must actually work and must be run before every start. The fuel system, from a fuel tank that is boxed in where you cannot inspect it, to six-decade-old hoses and fittings, is one of the first things to check and one of the most dangerous to ignore. And on any older inboard boat, carbon monoxide from the exhaust can find its way into the cabin and the bridge. None of this should scare you off. It should simply be treated as real. Where the boat can hurt you or your wallet, this book errs toward caution, and so should you.

Now, go find out exactly which Bertram 31 is yours. The rest of the book is waiting on that answer.

The Bertram 31 is one of those rare boats whose story is inseparable from the boat itself. Owners do not just run a 31, they carry a piece of powerboat history, and understanding where the hull came from will change how you look at every frame, strake, and hull number. This chapter covers the origin story, the production years, the many configurations, how to identify what you actually have, and where the boat sits today in reputation and value. It also draws a hard line between the classic 31 and the modern Bertram 35, which is a different boat entirely.

2.1 The Hull That Started It All

Every Bertram 31 traces back to one idea: the deep-v hull. The concept belongs to C. Raymond "Ray" Hunt, a Massachusetts sailor and designer broadly credited as the father of the modern deep-V (source: Soundings, "The Dean of Deadrise"). His radical notion was a hull with a constant, steep V-shaped bottom carried all the way from the bow to the transom, combined with longitudinal strake running fore and aft to knock down spray and add lift. This was a sharp break from the flat-bottomed aft sections that most planing powerboats used at the time, sections that ran fast in calm water but pounded brutally and slammed sideways in a chop (source: bertram31.com/history).

The man who saw the potential was Richard H. "Dick" Bertram, a Miami yacht broker and accomplished racing sailor. The pivotal moment came at the 1958 America's Cup trials off Newport, Rhode Island. Bertram watched a small Hunt-designed fiberglass deep-V being used as a tender to the 12-Metre yacht Easterner and was struck by how well the little boat handled the seas (source: bertram31.com/history; Yachting, "The Legacy & the Legend"). One account describes a roughly 23-foot prototype cutting cleanly through 6-foot seas off Newport that year (source: Yachting, "The Legacy & the Legend"). The fiberglass on Hunt's original tender was laid up by Bill Dyer (source: bertram31.com/history).

Bertram did not just admire the design. He licensed Hunt's plans and had a wooden deep-V of roughly 30 feet built as a race and utility boat, using cold-molded plywood construction. He named her Moppie, after his wife Pauline, who had carried the nickname since childhood (source: bertram31.com/history; YachtWorld, "Cult Classics"). The wooden Moppie carried a constant 24-degree deadrise running fore and aft (source: bertram31.com/history). [CONFLICT] Later production reviews often quote a slightly different deadrise figure, which is covered below, so treat the prototype and production numbers as close but not proven identical. [UNVERIFIED] Whether the wooden Moppie was dimensionally identical to the later production hull is not documented in the available histories.

A note on the "31" in the name. The prototype is described in different sources as a 30-foot wooden boat and as a 31-foot deep-V, and the production boat's true length overall is 30 feet 7 inches. These all refer to the same nominal boat. The "31" is the marketing and nominal length, not a literal measurement.

2.2 The 1960 Miami-Nassau Race

Reputations are built, not claimed, and the Bertram 31's was built in one of the roughest ocean races anyone could remember. In 1960 Moppie entered the Miami-Nassau ocean race, a run of roughly 160 to 184 miles across open water (source: bertram31.com/history; Soundings, "Legend of the Bertram 31"). [CONFLICT] The exact course distance is cited differently across sources, so treat it as a range. The conditions were savage: 8 to 12 foot seas and winds over 30 knots, described repeatedly as the worst in the event's history (source: bertram31.com/history; Soundings, "Legend of the Bertram 31").

Sam Griffith drove and worked the throttles while Carleton Mitchell navigated and later wrote the account for Sports Illustrated (source: bertram31.com/history). The crew's aluminum chairs crumpled at the start line, forcing the men to stand for the entire race. Only two V-hulls even finished; the rest turned back or limped in the next day. Moppie won and set a course record, with an elapsed time reported around eight hours and a margin of roughly two hours over the second-place boat (source: bertram31.com/history). [CONFLICT] One summary instead frames the win as beating the previous record by about four minutes, which measures the margin against the old record rather than the runner-up. [UNVERIFIED] The precise elapsed time and margin should be checked against a primary race record before being taken as exact. Griffith later called the boat "a breakthrough" (source: Soundings, "Legend of the Bertram 31").

The point that matters is not the stopwatch. It is that the deep-V hull proved itself in the worst possible water, in front of the entire sportfishing world, by winning rather than by advertising.

2.3 Founding of Bertram Yacht

The race publicity did the rest. Demand appeared almost overnight, and Dick Bertram famously explained that "there were so damn many yachtsmen waving checkbooks at me that I had to go into business" (source: bertram31.com/history; paraphrased in Yachting, "The Legacy & the Legend"). Bertram had a fiberglass version of Moppie's hull tooled up and launched the company in 1960 to 1961 (source: bertram31.com/history; Soundings, "Legend of the Bertram 31").

Production began in a rented warehouse in Hialeah, Florida, and Bertram Yacht's main operations settled in the Miami area (source: bertram31.com/history). The early workforce leaned heavily on skilled Cuban craftsmen who had fled Fidel Castro's regime, and Bertram credited them directly: "If it hadn't been for the Cubans, there probably wouldn't be a Bertram" (source: Soundings, "Legend of the Bertram 31"). The newly christened production model made its public debut at the 1961 New York (National) Boat Show, where crowds gathered around the strange deep bottom of the hull (source: Soundings, "Legend of the Bertram 31"; bertram31.com/history).

The historical claim that follows the boat everywhere is that the Bertram 31 was the first mass-produced deep-V, and the first to run the design successfully at offshore speeds (source: Soundings, "Legend of the Bertram 31"). In doing so it proved two things at once: that the deep-V concept worked in production, and that fiberglass could be built strong enough and seaworthy enough for serious offshore use (source: Miami Yacht Sales history summary).

2.4 Production History

The Bertram 31 stayed in the catalog for a remarkably long run. Regular production launched in 1961 and ended with the 1983 model year (source: bertram31.com/history; HMY Powerboat Guide, "Bertram 31 Flybridge Cruiser 1961-83"). [CONFLICT] Several sources describe the run as "16 years" even though 1961 to 1983 spans about 22 calendar years. The "16 years" figure likely refers to the years the model was actively promoted rather than the full calendar span, but the sources do not reconcile it cleanly. The safe and accurate phrasing for an owner is simply that the 31 was in production from 1961 to 1983.

How many were built is one of the genuine open questions of the boat's history. [CONFLICT] The most commonly cited figure is roughly 1,860 hulls, a number that two independent sources agree on (source: bertram31.com/history; Soundings, "Legend of the Bertram 31"). A dealer history instead reports 1,986 boats (source: Atlantic Yacht & Ship / Miami Yacht Sales summary), and other summaries round to "over 1,700" or "over 1,800." The best-supported figure to work from is about 1,860 built, with the understanding that the true total may be somewhat higher. The count of special-edition boats is also disputed: 23 by one account, 50 by another (source: bertram31.com/history; Atlantic Yacht & Ship summary). The community's own registry threads generally cite somewhere between about 1,860 and 2,000 hulls pulled from the single split mold (source: bertram31.com hull-number threads).

Corporate ownership changed hands during the run. The Whittaker Corporation acquired Bertram in 1968, after which the factory grew into one of the largest pleasure-boat builders in the world (source: Atlantic Yacht & Ship summary). [UNVERIFIED] The exact date and terms of the Whittaker acquisition should be corroborated against a formal Bertram corporate history before being treated as settled, and later plant addresses beyond the original Miami-area operations are not documented in the available sources.

Throughout its life the Bertram 31 was regularly described as one of the best-selling American production powerboats ever built, and as the workhorse of the sportfishing industry (source: Soundings, "Legend of the Bertram 31").

2.5 Configurations and Series

One hull, many boats. The 31 was offered in a series of configurations built off the common deep-V hull, and knowing which one you have is the first step in owning the boat intelligently. The community's specification page lists six configurations (source: bertram31.com/specs):

• Flybridge Cruiser (FBC): A cabin with a flybridge and an aft cabin bulkhead, giving an enclosed deckhouse. The more weather-protected cruising variant.
• Sport Fisherman (SF): A cabin with a flybridge but no aft bulkhead, leaving the cockpit open to the deckhouse. This is the classic convertible sportfisherman layout and the most iconic of the family.
• Bahia Mar: A small trunk cabin with an elevated helm.
• Express: A full cabin with a raised helm amidships.
• Moppie: An open configuration with a forward windscreen, named for the original race boat.
• Sedan: A sportfish-type cabin with inside controls and no flybridge.

[CONFLICT] Not every source groups the boats the same way. Soundings condenses the family into four models: Sport Fisherman, Flybridge Cruiser, Hardtop Cruiser, and Express Cruiser (source: Soundings, "Legend of the Bertram 31"). Period sales literature from December 1962 lists the lineup as Express Cruiser, Flying Bridge Sport Fisherman, Hardtop Sport Cruiser, and Convertible Sport Cruiser (source: 1960s Bertram 31 brochure via boatbrochure.com). Names like "Hardtop Cruiser" overlap with what other sources call the Sedan or Bahia Mar. For practical purposes, work from the fuller six-way list and expect to meet the same boats under different names.

The most useful division for an owner is simpler than the model names: open versus enclosed. The open boats (Sport Fisherman and Moppie) leave the cockpit and helm exposed and are prized by fishermen. The enclosed boats (Flybridge Cruiser, Sedan, Express) trade some of that openness for weather protection. The convertible Sport Fisherman with a flybridge is generally the most collectible and the most sought-after of the group.

2.6 How to Identify What You Have

Sorting out a specific boat comes down to a few things you can check directly.

Hull configuration. Start with the deckhouse and helm. Is there a flybridge, or are the controls down low? Is the cockpit open to the deckhouse (Sport Fisherman) or closed off by an aft bulkhead (Flybridge Cruiser)? Is the boat fully open with just a windscreen (Moppie)? These visual cues place the boat in the configuration list above faster than any paperwork.

Hull number and year. The classic 31 was laid up from a single split mold across the whole run, so the hull itself does not tell you the year at a glance. The most reliable path is the hin hull identification number together with the community hull-number registry maintained on the owner's forum, where owners log hull number, year, and boat name (source: bertram31.com hull-number threads). This registry is the closest thing to an official record of the fleet, though it is a running forum thread rather than a formal database.

Fuel capacity as a rough date clue. Early boats carried roughly 170 to 175 gallons of fuel; capacity was later increased to 222 gallons (source: bertram31.com/specs; BoatUS review by Jack Hornor). [CONFLICT] The year of the increase is cited as 1968, 1971, or 1972 depending on the source, so tankage is a hint rather than proof. Verify against a factory brochure if the exact year matters.

Engines are not a reliable identifier. Most 31s left the factory on twin gasoline inboards, but the fleet has been repowered so extensively over 40-plus years that what is in the bilge today tells you very little about the original build. Treat the engines as a separate question from identity, covered in its own chapter.

When in doubt, the fastest resolution is to post the hull number and a few photos to the owner's community, where experienced members routinely place a boat by its details.

2.7 Reputation, Then and Now

The Seakeeping Legend

The phrase "rides like a Bertram" entered the language for a reason. The deep-V hull resisted broaching, prevented prop-walking in beam seas, and excelled at running inlets, all in conditions that stopped flatter boats cold (source: Soundings, "Legend of the Bertram 31"). Yachting described the hull as one that "levels head seas and tracks down sea as though she were on rails," and noted that salesmen would demonstrate its stability by running in big seas with no hands on the wheel (source: Yachting, "The Legacy & the Legend"). The often-quoted value to a fisherman is that the 31 made "fishing days that were marginal comfortable, and days that were out of the question doable" (source: Yachting, "The Legacy & the Legend").

The Honest Caveats

A credible owner's reference does not sell the legend without the fine print. The 31 has real trade-offs, and knowing them makes you a better skipper.

It is a wet boat. As surveyor David Pascoe put it bluntly, it is "big time wet, because it's got a full bow with little flare" (source: David Pascoe, yachtsurvey.com). Modest bow freeboard of around 44 inches and minimal bow flare mean spray comes aboard (source: BoatUS review by Jack Hornor). It also rolls noticeably in a beam sea, a direct consequence of the narrow, deep hull form (source: BoatUS review by Jack Hornor). And its realistic speed into a head sea is modest: Pascoe observed that the boat "is not going to carry 22 knots into a three-foot head sea. You'll get by with 16 knots" (source: David Pascoe, yachtsurvey.com). The deep-V also consumes significant horsepower to push, which feeds directly into the fuel-thirst reputation of the gas-powered boats (source: Yachting, "The Legacy & the Legend").

It is worth noting that this is a moderate deep-V, not an extreme one. The 11-foot-2-inch beam without chine flats, the light displacement, and the engines mounted low and amidships give the boat a low center of gravity and keep it a sensible, seaworthy hull rather than a punishing race platform (source: David Pascoe, yachtsurvey.com).

Its Place in Sportfishing History

Collectors and historians prize the 31 for three consistent reasons: it was the first mass-produced deep-V that worked at offshore speed, it proved itself by winning races rather than by marketing, and it demonstrated that fiberglass could be both strong and seaworthy (source: Miami Yacht Sales history summary). Well-kept hulls from the 1960s and 1970s still actively fish and cruise, especially in Florida waters, and a large restoration and enthusiast community treats the boat as a platform worth serious investment (source: David Pascoe, yachtsurvey.com). It is repeatedly called a cult classic and one of the most iconic powerboats ever built (source: YachtWorld, "Cult Classics").

2.8 The Modern Bertram 35: Not the Same Boat

This is the single most important point of clarification in the whole history, and it trips up buyers constantly. The classic Bertram 31 and the modern Bertram 35 are different boats.

The Bertram brand changed hands several times after the classic era, passing to the Ferretti Group in 1998 and then to Italy's Gavio Group, with the sale closing on March 31, 2015 (source: boatinternational.com, "New ownership for Bertram Yachts"). Under Gavio ownership, Bertram revived the concept of the 31 as the Bertram 35 Flybridge, an explicit modern tribute to the original (source: Yachting; PowerYacht summary). It was announced to the press around 2016 to 2017, developed from 2017, and the first hull came off the line around 2018 (source: PowerYacht blog; itBoat summary). The 35 was drawn by designers Michael Peters and Marty Lowe, with the stated goal of keeping the "classic Bertram DNA intact" while fitting modern propulsion, and nine units sold on plan before launch (source: PowerYacht/itBoat summary).

Two things to be crystal clear about. First, there was no like-for-like reissue of the classic 31 itself. The revival is a larger, modernized 35, not a return of the original boat to production. Second, the 35 is a modern build and is not parts-compatible with the classic 31. Nothing in this book about the classic hull, its hardware, its systems, or its restoration applies to the 35. If you are shopping and see a "Bertram" priced far above the classic range, check the model and year before anything else, because a new-era 35 sells in the neighborhood of $595,000 to $699,000 (source: boats.com / Boat Trader summary), a completely different market from the vintage boat.

2.9 Current Collector and Used-Market Values

The classic 31 market is condition-driven and thin, which makes single "book values" unreliable. Prices are best understood as ranges tied to the state of restoration.

Broad listing aggregators show enormous spreads, from roughly $24,900 to $595,000, with a reported average around $122,500 (source: Boat Trader summary). Those numbers come with a serious caveat: the very top of that range almost certainly includes modern Bertram 35 listings swept in by the make-and-model filter, not classic 31s, so the realistic ceiling for a vintage boat is lower.

Real-world asking prices for classic boats give a clearer picture. A 1981 Bertram 31 in Port Aransas, Texas was asking $125,000 in early 2025, and a restored 1973 example in Englewood, Florida was asking $199,000 in the fall of 2025 (source: Denison Yacht Sales listings). For historical anchoring, a 1969 boat that originally sold for about $22,000 is now described as worth many times that (source: Yachting, "The Legacy & the Legend").

Pulling it together, a realistic framework for the classic 31 looks like this. Solid drivers that need nothing urgent commonly run in the $40,000 to $90,000 range. Clean, updated boats sit around $100,000 to $150,000. Fully restored and repowered showpieces reach $150,000 to $200,000 and beyond. [UNVERIFIED] These figures reflect 2024 to 2025 asking prices rather than closed sales, and precise current values should be confirmed against live listings. The key insight for a buyer is that condition and the quality of any restoration or repower matter far more than the model year, and that a cheap 31 with a saturated core or failed tanks can cost more to make right than a more expensive turnkey boat.

2.10 Why This History Matters to an Owner

The Bertram 31 is not a boat you own casually. Its value, its handling, and its restoration economics all flow directly from the history in this chapter: a deep-V hull proven in a brutal ocean race, built in large numbers over two decades from a single mold, offered in a handful of configurations, and now cherished as a restoration platform. Knowing which variant you have, what year it likely is, and where it sits in the market puts you in a position to make good decisions about everything that follows in this book. And knowing that the modern 35 is a separate boat keeps you from making an expensive mistake before you even step aboard.