Boström 37

Blue-water Scandinavian cruiser

The Swedish classic with a Hallberg‑Rassy soul

Discover the Boström family—1970s Scandinavian designs pairing legendary build quality with modern, effortless sailing.

Explore heritage & designProven at sea

Models

Boström models

Two proven Scandinavian cruisers sharing the same blue‑water DNA, sized for different crews and adventures.

Boström 31 (B-31)

Compact, capable and efficient—an offshore‑ready 31‑footer with a skeg‑hung rudder and moderate displacement.

  • Designer: Bruno Boström
  • Rig: Masthead sloop
  • Hull/Rudder: Fin keel, skeg‑hung rudder
  • Built: From 1973 (Mk I); Mk II from 1977–1984
  • LOA: 30.64 ft (9.34 m)
  • Beam: 9.06 ft (2.76 m)
  • Draft: 5.91 ft (1.80 m)
  • Displ/Ballast: 7,782 / 3,748 lb (3,530 / 1,700 kg)
Boström 31 Mk II design drawing
Boström 31 Mk II under sail

Mk I vs Mk II (B31)

  • Mk II keeps the same underwater hull but adds more freeboard and a new deck.
  • Reports note a wider, deeper cockpit, added anchor locker, and more headroom below.
  • Mk I fit‑out quality varies (many were owner‑completed); Mk II generally more consistent.

Ratio highlights: SA/D ~15.1 • D/L ~198 • Comfort ~23.3 • CSF ~1.83. Balanced and seakindly for coastal and offshore work in a smaller package.

Background: The B‑31 emerged in the early 1970s and, after early prototype tweaks by sailors Tom Sifvert and Bengt Sögerberg (deeper keel, longer hull, taller rig), it began winning races and found a strong family following. Built to Lloyds‑influenced standards with a thick FG hull and reinforced keel, later Mk II production in Denmark ("Starboat") added headroom and a larger cockpit with more standardized interiors.

Ergonomics & value: Owners describe a narrow‑but‑long cockpit with great helm control, very stiff/forgiving manners, and “most boat for the money.”

View B31 Mk I specsView B31 Mk II specsRead owner quotesWatch B31 walkthrough

Boström 37 (B-37)

rare • ~300 built

The bigger sister—known for its robust build, hybrid center‑cockpit and private aft cabin, with true blue‑water range.

  • Designer: Bruno Boström
  • Rig: Masthead sloop
  • Hull/Rudder: Fin keel, skeg‑hung rudder
  • Built: From 1974 (~300 built, scarce)
  • LOA: 36.25 ft (11.05 m)
  • Beam: 12.83 ft (3.91 m)
  • Draft: 6.40 ft (1.95 m)
  • Displ/Ballast: 17,637 / 7,716 lb (8,000 / 3,500 kg)

Ratio highlights: SA/D ~15.9 • D/L ~291 • Comfort ~28.6 • CSF ~1.98. Offshore‑oriented stability and comfort with long‑passage capability.

Upgrade case from B31: the B‑37 carries provisions, water and gear with less performance penalty, stays more comfortable at sea (higher CR, longer waterline), and adds a true private aft cabin for off‑watch rest. For extended cruising or higher resale interest due to ~300 built, it’s often worth the premium.

Owner notes: “stable and solidly constructed”, “out‑sails newer boats in 10–20 m/s”, and an honest 5–6.8 kn under power. See History for sourced quotes.

Boström 37 exterior design drawing
Boström 37 exterior photograph
Boström 37 interior photograph
View detailed specsRead owner quotes

Figures compiled from publicly available sources such as sailboatdata.com; verify against your specific hull and build year.

Heritage

A Legacy Forged in the North Sea

The Genius of Bruno Boström

Bruno Boström was a visionary, years ahead of his time. He didn't just create another boat for the era; he meticulously synthesized the best attributes from the most legendary Scandinavian brands, taking all the good things from Rassy, Swan, and Najad and rolling them into one design.

The Hallberg‑Rassy Connection: Shared DNA

The Boström 37 was built by Porali Marin in Sweden, a yard associated with building robust hulls also supplied to Hallberg‑Rassy. The hybrid center‑cockpit closely mirrors the Rassy approach, elevating Boström to a quietly world‑class pedigree.

Built Without Compromise

The boat's formidable construction—often cited with Lloyds‑style standards—is tangible proof of offshore purpose: 'way over‑built, but not heavy'. Designed to survive a 360° rollover and keep going.

Design

The Art of Intelligent Design

The Perfect Cockpit: Safe, Social, and Smart

The hybrid center‑cockpit sits just far enough forward to allow an aft cabin and avoid being pooped, yet not so far as to be wet—producing a dry, secure motion. On the B37 it enables a true private aft cabin; on the B31 it keeps a deep secure cockpit while maximizing interior volume.

Effortless Power, Balanced Performance

Most driving power lives in the foresail. The tall, narrow main is easily reefed—often not even required. In rising wind you reduce sail safely from the cockpit by rolling the jib. Balanced under a 135% furling genoa alone, the boat makes 6–7 kn in 15–20 kn breeze.

Confidence in Any Sea

A fin keel with a protective skeg‑hung rudder combines performance with steering protection. It's a promise of reliability and control when far offshore.

Voyage

Proven by the Ultimate Test: A Circumnavigation

The true measure of a blue‑water yacht isn't found in specifications alone, but in the stories etched into its logbook. Among Boström owners, one notable example is a Boström 37 used for an epic circumnavigation by renowned Norwegian author and journalist, Ragnar Kvam Jr.

In 1987, Kvam sold everything he owned and chose a Boström 37 for the most demanding adventure of all: a voyage around the world. He named her "Northern Quest," and for the next 14 years, she was his home and his vessel for exploring the planet. His choice of the B37 was a deliberate one, selecting a boat built to withstand anything the world's oceans could throw at it.

Kvam chronicled his incredible journey in a bestselling trilogy of books, cementing both his legacy as an adventurer and the Boström reputation for trustworthy long‑distance cruising. These books offer an intimate, open‑hearted account of life at sea and stand as a testament to the design's capabilities.

Read the "Northern Quest" Trilogy:

The Modern Classic: a canvas for your adventure

A home on the water

Boström yachts are known for exceptional livability. On the B37, a private aft cabin provides a quiet, stable retreat under way and in harbor, while the generous salon and 6'4"/1.95 m headroom make life aboard comfortable for taller crew members. The B31 delivers a simpler, efficient layout with surprising volume for a 31‑footer.

Timeless foundation, modern soul

With exceptionally strong, over‑built hulls, Boström boats are ideal resto‑mod platforms—easy to personalize without compromising their offshore pedigree.

The B31 in particular pairs a tall, efficient masthead rig with a dry, secure cockpit and famously rugged keel structure—qualities that continue to win converts decades on.

History

Heritage and timeline

The Boström line was conceived by Swedish designer Bruno Boström as practical, seaworthy cruisers with moderate displacement, skeg‑hung rudders and masthead rigs. The 31 arrived first, followed by a larger 37 sharing the same blue‑water philosophy.

Designer

  • Bruno & Börje Boström — Swedish yacht designers behind the Boström line (active 1970s–80s). Bruno is typically cited as principal designer; Börje as co‑designer and for production refinement.
  • Design philosophy: practical blue‑water cruisers with moderate displacement, high stability, predictable handling.
  • Rigs & structure: conservative masthead sloop plans sized for real‑world weather; robust Nordic fiberglass layups (often Lloyd’s‑style specs).
  • Layout thinking: B‑31 optimized for compact offshore cruising; B‑37 added hybrid center‑cockpit and true aft cabin without losing seakeeping.

Boström 31 (B‑31)

  • First built: 1973.
  • Mk II variant: 1977–1984; same underwater hull, more freeboard and new deck/cockpit.
  • Role: compact offshore‑capable cruiser with balanced ratios.
  • Early prototypes refined by sailors Tom Sifvert & Bengt Sögerberg—deeper fin keel, a touch more length, taller rig unlocked race wins and popularity.
  • Built to Lloyds standards with thick fiberglass hull and reinforced keel attachment; tall masthead rig suits lighter Scandinavian winds.
  • Production expanded to Denmark ("Starboat"). Mk II added headroom & larger cockpit; Danish yards standardized teak/mahogany interiors.
  • Known for dry, secure cockpit and “sails like a train” handling; many examples still actively cruised.

Notes: Many Mk I hulls sold bare or as kits; interior fit varies. Mk II more consistent with practical additions (anchor locker, headroom).

Boström 37 (B‑37)

  • First built: 1974.
  • Numbers built: approximately 300 (rare).
  • Builder: Porali Marin AB (Sweden).
  • Robust Scandinavian fiberglass layup (often Lloyd’s cited) around a fin keel & skeg‑hung rudder. Hybrid center‑cockpit enables true private aft cabin.
  • Original engine: Volvo Penta ~45 hp diesel (see Specifications).
  • Role: offshore‑oriented cruiser with more comfort & load‑carrying than B‑31 while retaining handling & safety.
  • Performance (owner‑reported): stable, out‑sails many newer boats in strong winds; ~5 kn cruising revs, up to ~6.8 kn full throttle (see quotes).

Widely regarded as a step up from the B‑31 for crews wanting more load‑carrying, passage comfort & private aft cabin—without losing rugged build & handling.

Boström 37 exterior and interior design drawings
Boström 31 Mk II design drawing

B31 owner impressions

  • “Safe and stable… terribly stiff and seaworthy… one can sail around the world with no problems!” — YBW Forum
  • “The cockpit is narrow but long… sits nicely at the wheel with full control!” — YBW Forum
  • “Most boat for the money, I think!” — YBW Forum

See also: Owner walkthrough (YouTube) for additional perspective.

B37 owner & user impressions

  • “Stable and solidly constructed.” source
  • “Very nice sailor — out‑sails most newer boats in 10–20 m/s wind.” source
  • “Makes 6.8 knots at full throttle; around 5 knots at cruising revs.” source
  • “A seagoing, safe cruising yacht with spacious accommodation and a large centre cockpit.” source
  • “Way over‑built, but not heavy.” source

Sources: sailboatdata.com; owner reports (YBW Forum); B31 walkthrough (YouTube). Specs vary by year and refit.

B31 vs B37 at a glance

Both boats share Boström DNA: moderate displacement, skeg‑hung rudder and offshore intent. The 37 adds space, load‑carrying and long‑passage comfort.

SpecBoström 31Boström 37
LOA30.64 ft (9.34 m)36.25 ft (11.05 m)
Beam9.06 ft (2.76 m)12.83 ft (3.91 m)
Draft5.91 ft (1.80 m)6.40 ft (1.95 m)
Displ / Ballast7,782 / 3,748 lb17,637 / 7,716 lb
Sail Area (100%)370 sq ft671 sq ft
Key ratiosSA/D ~15.1 • D/L ~198 • CR ~23 • CSF ~1.83SA/D ~15.9 • D/L ~291 • CR ~28.6 • CSF ~1.98

Which one for you?

  • B31: simpler systems, lower costs, easier berthing, capable of offshore passages with prudent loading.
  • B37: more tankage and storage, private aft cabin, higher comfort at sea, better load‑carrying for long cruises.

Why step up to a B37

  • Scarcity & desirability: ~300 built—often stronger resale interest and owner demand.
  • Comfort under way: longer waterline and higher Comfort Ratio smooth out passages and watch‑keeping.
  • Real separation of spaces: private aft cabin lets crew rest properly off‑watch.
  • Load‑carrying done right: more tankage and volume to carry cruising gear without bogging down.
  • Same DNA, more range: retains skeg‑hung rudder and rugged layup with true blue‑water legs.

Specs and ratios from sailboatdata.com; confirm details on your hull and year.

Specs

Specifications

Boström 31

FeatureImperialMetric
Length Overall (LOA)30.64 ft9.34 m
Length Waterline (LWL)25.98 ft7.92 m
Beam9.06 ft2.76 m
Draft5.91 ft1.80 m
Displacement7,782 lb3,530 kg
Ballast3,748 lb1,700 kg
Sail Area (100% Fore+Main)370 sq ft34.4 m²
Original EngineYanmar diesel—
RatioValueWhat this means
Ballast / Displacement48.16%Very stiff and stable for size; stands up to breeze and reduces heel.
Displacement / Length198Moderate displacement for a seakindly motion and forgiving handling.
Comfort Ratio23.3Appropriate for coastal/offshore passages on a compact platform.
Capsize Screening1.83Below 2.0—indicative of offshore suitability.
Sail Area / Displacement15.1Balanced power—good everyday performance without being over‑canvased.

Boström 31 Mk II

Same underwater hull as Mk I, with more freeboard and a redesigned deck/cockpit. Widely reported to have a wider, deeper cockpit, added anchor locker, and increased headroom below.

FeatureImperialMetric
Length Overall (LOA)30.61 ft9.33 m
Length Waterline (LWL)25.98 ft7.92 m
Beam9.06 ft2.76 m
Draft5.91 ft1.80 m
Displacement7,275 lb3,300 kg
Ballast3,638 lb1,650 kg
Sail Area (100% Fore+Main)370 sq ft34.4 m²
Original EngineYanmar diesel—
RatioValueWhat this means
Ballast / Displacement~50%Slightly higher than Mk I; very stiff for the size.
Displacement / Length~185Marginally lighter for the same LWL; still moderate.
Comfort Ratio~21.8A touch lower due to reduced displacement, still offshore capable.
Capsize Screening~1.87Below 2.0—indicative of offshore suitability.
Sail Area / Displacement~15.8A bit more power per pound than Mk I.

Boström 37

FeatureImperialMetric
Length Overall (LOA)36.25 ft11.05 m
Length Waterline (LWL)30.02 ft9.15 m
Beam12.83 ft3.91 m
Draft6.40 ft1.95 m
Displacement17,637 lb8,000 kg
Ballast (Lead)7,716 lb3,500 kg
Sail Area (100% Fore+Main)671 sq ft62.34 m²
Original EngineVolvo Penta 45 hp diesel33.6 kW
RatioValueWhat this means
Ballast / Displacement43.75%High stability and stiffness; confidence in heavy weather.
Displacement / Length291Moderate‑heavy for gentle motion on ocean passages.
Comfort Ratio28.6Comfortable motion suitable for blue‑water cruising.
Capsize Screening1.98At the offshore threshold—ample ultimate stability.
Sail Area / Displacement15.9Sufficient power for passagemaking without demanding large crews.
Boström 37 exterior profile drawing
Boström 37 interior plan and profile

Sources: sailboatdata.com and public owner reports. Specs vary by year and refit—confirm on your hull.

Connect

Is a Boström your next chapter?

Boström yachts aren't for everyone—they're for sailors who value hidden Scandinavian quality, proven offshore safety, and intelligent rigs that make short‑handed sailing relaxed. If you believe the best boats are the ones you discover—not the ones marketed to you—this may be your yacht.

Become Part of the Legacy

Built in limited numbers in Sweden, these boats are sailed worldwide by owners who value strength, intelligence, and grace. Explore the market, connect with the community, and consider becoming a steward of this rediscovered lineage.

Connect with the Boström community

Join B31 and B37 owners and enthusiasts in our Facebook group for discussions, advice, and shared experience.

Visit the Boström Fan Group

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