Mamba 311 Information, Review, Specs

Sailing Performance & Handling

The sailing characteristics of the Mamba 311 are defined by its high ballast ratio and stiff hull. According to official technical ratings from Svensk Segling, the boat features a displacement of approximately 3,500 kg with a 1,600 kg lead fin keel. This 46% ballast-to-displacement ratio is remarkably high for a 30-foot cruiser, resulting in a vessel that remains upright and composed well into the upper wind ranges. Its Displacement/Length (D/L) ratio of roughly 191 categorizes it as a "moderate racer," balanced enough to serve as a family cruiser while retaining sufficient agility for club racing.

Under sail, the Mamba 311 is known for being responsive and light on the helm. Unlike its predecessor, the 311 was commonly fitted with a taller 7/8 fractional rig with swept spreaders. This configuration allows for a larger mainsail and a smaller, more manageable headsail, making the boat easier to handle for short-handed crews. Owners often note that the boat glides exceptionally well in light air—a common trait for Bengt Karlsson designs—while the deep spade rudder provides precise control when reaching. The absence of a skeg on the rudder (which was present on the original Mamba 31) further reduces drag and increases maneuverability in tight quarters.

Interior Comfort & Variations

The transition from the Mamba 31 to the 311 brought substantial improvements to the living experience. The most significant change was a redesigned deck that provided approximately 8 cm of additional headroom, bringing the total standing height in the salon to a comfortable 1.85 meters. The interior layout shifted away from the "dinette" style found on many 1970s boats toward a more conventional and seaworthy L-shaped galley located to port of the companionway.

The cabinetry is typical of high-quality Swedish production from the era, featuring warm teak joinery without the extensive use of fiberglass liners, which gives the cabin a traditional, woody feel. The 311 accommodates 5 to 6 berths, including a forward V-berth, a double aft berth tucked behind the navigation station, and salon settees. A notable variation in production included the choice between the standard 7/8 fractional rig and a masthead rig; while the fractional version is more common and favored for its trimability, the masthead rig provides a simpler, more robust setup for offshore passage-making.

The Mamba 311 is part of a broader family of Swedish yachts. Its closest relative is the Mamba 31, which shares the same underwater profile but features a lower coachroof and a different interior. Larger siblings include the Rolf Magnusson-designed Mamba 34 and 341, which follow a similar design philosophy but offer true three-cabin layouts and increased blue-water capabilities.

Known Issues & Buyer’s Checklist

Prospective buyers should approach the Mamba 311 with a focus on its age-related structural integrity and mechanical systems:

• Deck Core Integrity: The deck is a sandwich construction using Divinycell or Balsa as a core material. Owners on technical forums have noted that moisture can penetrate around deck fittings, stanchions, and the mast step if the sealant has failed. Percussion testing with a phenolic hammer is essential to check for delamination.
• Engine Maintenance: Many units were originally equipped with the Volvo Penta MD7A or the later MD2002. These engines are reliable but often raw-water cooled; buyers should inspect the heat exchanger (if fitted) and the internal cooling passages for salt-water corrosion or blockage.
• Rudder Bearings: The spade rudder is highly responsive, but the bearings can develop play over decades of use. Check for "slop" in the steering and inspect the rudder blade for any signs of water ingress or "wicking" at the edges.
• Rigging Tension: On fractional rigs with swept spreaders, the mast relies heavily on shroud tension rather than a backstay for stability. Inspect the chainplates and the mast step for signs of compression or stress cracking in the gelcoat.

Community & Resources

The Mamba community is primarily centered in Northern Europe, where the boats were most prolific. The Mambaförbundet (Mamba Association) serves as the primary technical repository for the model, offering original sail plans, wiring diagrams, and owner-led advice on modifications. Technical specifications and handicap data are also regularly maintained by the Swedish Sailing Federation to support owners continuing to race in SRS (Svenskt Respitsystem) events.

The Verdict

The Mamba 311 is a quintessential Swedish cruiser-racer that offers more sophistication and interior volume than its predecessor while maintaining the stiff, seaworthy performance Karlsson is known for.

Pros:

• High ballast ratio (46%) ensures exceptional stability and safety in heavy weather.
• Superior interior headroom (1.85m) for a 30-foot boat of its era.
• Lead keel as standard, which provides better performance and lower maintenance than iron.
• Highly responsive handling with the 7/8 fractional rig.

Cons:

• Aft berth can feel cramped compared to modern wide-transom designs.
• Spade rudder lacks the protection of a skeg.
• Older Volvo Penta engines may require significant maintenance or repowering.