Southerly 135 Mk I Information, Review, Specs

Sailing Performance & Handling

The sailing characteristics of the Southerly 135 Mk I are defined by its variable draft, which transitions from a shallow 0.84m (2’9”) to a deep, performance-oriented 2.41m (7’11”). When the aerofoil-shaped cast iron keel is fully lowered, the boat gains a high-aspect-ratio foil that provides exceptional lift and pointing ability. Unlike many shallow-draft vessels that struggle to windward, the 135 handles more like a fixed-keel yacht, benefiting from the design work of Humphreys Yacht Design, which optimized the hull for offshore stability.

With a displacement of approximately 11,500kg and a moderate sail area-to-displacement ratio, the 135 Mk I is a steady, predictable performer rather than a light-wind flyer. It tracks well in a seaway, aided by its substantial displacement and a well-balanced hull form. Handling under power is facilitated by the twin-rudder configuration common to many Southerlys, which ensures the boat remains controllable even when the keel is retracted. However, the windage of the high-sided hull and center-cockpit layout requires attentive handling during low-speed maneuvers in tight marinas.

Interior Comfort & Variations

The interior of the Southerly 135 Mk I is characterized by the brand’s signature raised-saloon layout, which provides panoramic views through the deckhouse windows and allows for an internal steering station or a well-protected navigation area. The use of high-quality teak or cherry joinery was standard, creating a warm, traditional nautical atmosphere. Because the engine is situated under the saloon floor, the layout maximizes living space in the ends of the boat.

The Mk I was typically offered in two primary configurations: a luxury two-cabin layout and a three-cabin family version. In the two-cabin variant, the aft cabin is a cavernous master suite with a centerline island berth and ensuite heads, making it a favorite for live-aboard couples. The three-cabin version incorporates a smaller twin-bunk cabin, often located on the port side forward of the saloon. Throughout all variations, the 135 Mk I is noted for its generous headroom, often exceeding 6’4” in the main saloon, and extensive storage capacity required for long-term cruising.

While the 135 Mk I is the primary focus, it is important to note its sibling, the Southerly 135 Mk II. The Mk II introduced a revised "sugar scoop" transom with an integrated bathing platform, extending the overall length slightly and modernizing the exterior profile. Internally, the Mk II often featured updated electrical systems and minor adjustments to the galley layout, though both marks share the same proven hull and keel mechanics.

Known Issues & Buyer’s Checklist

Prospective buyers of a Southerly 135 Mk I should prioritize a technical inspection of the swing-keel mechanism, which is the heart of the vessel.

• Keel Ground Plate: The massive cast-iron assembly that sits flush with the hull is a structural component. Inspectors should look for signs of "wicking" or rust-jacking between the plate and the GRP hull, which can indicate that the sealant has failed.
• Hydraulic System: The keel is operated by a hydraulic ram and pennant system. It is vital to check the age and condition of the hydraulic hoses and the ram seals. Any "creep" (the keel slowly lowering or raising on its own) suggests a valve or seal failure.
• Keel Pivot Bolt: Though robust, the pivot bolt and its associated bushings are wear items. Evidence of "clunking" when the boat is in a seaway often points to worn bushings that require the boat to be hauled and the keel dropped for service.
• Window Seals: The large deckhouse windows are a defining feature but are prone to leaks as the original bedding compounds age. Evidence of water staining on the woodwork below the windows is a common find in older Mk I models.

Community & Resources

The primary hub for technical support and owner camaraderie is the Southerly Owners Association (SOA). This organization maintains an extensive technical library that includes historical manuals, wiring diagrams, and member-contributed "fixes" for common Northshore Yachts issues. The SOA is widely regarded as one of the most active owner groups in the UK, frequently organizing rallies that highlight the "beaching" capabilities of these unique yachts.

The Verdict

The Southerly 135 Mk I remains a premier choice for sailors who refuse to be limited by water depth but demand a yacht capable of crossing oceans. Its Humphreys-designed hull ensures it is a "real" sailboat, while its interior volume rivals much larger vessels.

Pros:

• Unrivaled Versatility: The ability to beach the boat or enter shallow lagoons opens up cruising grounds closed to 95% of other 45-foot yachts.
• Blue Water Build: High-quality construction and a center-cockpit design provide a sense of security in heavy weather.
• Interior Volume: The raised saloon and large aft cabin make it an ideal platform for long-term living aboard.

Cons:

• System Complexity: The hydraulic swing keel adds a layer of maintenance and inspection not found on fixed-keel boats.
• Engine Access: While the central location is good for weight distribution, accessing certain components can be tight compared to walk-in engine rooms.
• Market Premium: Due to their unique niche and the reputation of Northshore Yachts, they tend to command higher resale prices than mass-production cruisers of the same era.