Design and Development
Northshore Yachts of Chichester introduced the Southerly line in 1975 with the original intent that each boat be able to dry out in the tidal estuaries around the United Kingdom while retaining good stability and performance. The Southerly 110 arrived in 1983, and it evolved into the 37-foot Southerly 115 with more interior space and a center cockpit. The first version, the Mk I, carried a drop keel shaped as a triangular airfoil and a single shallow rudder to match the keel-up draft, but that rudder showed a tendency to ventilate as the boat heeled under certain conditions — a real-world flaw that prompted Northshore to commission British designer Rob Humphreys to rework the platform.
Humphreys, known for many successful designs including Dame Ellen MacArthur's Open 60, Kingfisher, deepened the keel to provide greater depth and lift and fitted twin rudders to maintain shallow draft while providing directional control under heel. The Mk II, III, and IV followed in sequence. Further modifications in subsequent marks were above the waterline and did not affect sailing qualities, meaning the hydrodynamic solution Humphreys reached has remained the defining character of all later boats.
Construction
The hull below the waterline is solid hand-laid-up fiberglass, with balsa coring used in the topsides and deck except in load-bearing areas, where plywood core was substituted. Hull and deck are joined at the top of a bulwark with a through-bolted flange that was also chemically bonded, capped with a teak rail. The keel arrangement is layered: internal ballast in the Mk I was a cast-iron pancake weighing 4,962 pounds, with the hydraulically operated 2,016-pound swing keel bringing total ballast to 6,978 pounds; the Humphreys modifications raised the aggregate to 7,597 pounds, providing meaningful righting moment when the keel is fully deployed. The Lewmar Torque Tube steering, considered almost bulletproof and overkill for a moderate-displacement vessel, is one indicator of the quality mindset of the builder, and the general standard of mechanical and electrical installation is described as above average.
Rig and Sail Handling
The 115 carries a deck-stepped Seldén double-spreader aluminum mast supported by a compression post in the cabin. Shroud geometry is tidy: a single chainplate anchors upper and intermediate shrouds on each side deck, with lowers attaching to a separate chainplate aft. The wide cabin trunk does restrict side-deck space, but because the chainplates are all inboard toward the cabin trunk, there is adequate width for crew to pass outboard of the shrouds. The backstay splits above the stern to port and starboard chainplates, tensioned by a simple block-and-tackle. The Seldén boom features internal reefing lines and is fitted with a Seldén rigid vang, a detail that keeps the working rig clean and the slab-reefing process straightforward for a shorthanded crew.
Under sail, the twin-rudder arrangement rewards the sailor who commits to using the boat as designed. Sailing to 35 degrees apparent wind at 5.5 knots, only a light touch on the wheel was needed to counteract a desirable slight weather helm. On a beam reach the boat moved at just over 6 knots with smooth, precise control. The boat performed in a manner similar to a fixed-keel boat and is a platform that can provide decent sailing performance and yet still allow access to many areas that deeper-draft boats cannot reach.
Accommodations
The center-cockpit layout delivers a level of privacy and space that belies the boat's 37-foot length. Forward, instead of a cramped V-berth, the 115 has an over/under configuration with two comfortable single berths, served by portlights on each side and an overhead hatch. The saloon is spacious with good headroom beneath the raised cabintop; a U-shaped settee to port surrounds a table supported on the compression post, with a settee completing the seating to starboard. The keel trunk is cleverly incorporated into the interior to minimize interference, beginning just aft of the compression post and rising to join with the galley counter. The L-shaped galley to port of the companionway offers ample counter space, drawers, a front-opening refrigerator, and a two-basin sink with a teak cover. Aft of the companionway, a step up leads to a spacious owner's stateroom with a berth that is nearly king-size — an unusual luxury in a 37-foot boat. As with all Southerly models, the overall fit and finish of the cabinetry is above average.
Known Issues and Surveyor Findings
Several recurring findings emerge from survey and ownership experience. The cast iron swing keel and plate need to be periodically refinished, as rust will eventually start to work its way through the primer and barrier coats — a maintenance obligation that distinguishes the 115 from simpler fixed-keel boats and demands attention at each haulout. The conventional shaft seal installed at the factory used a light gauge bronze/brass hose barb that becomes fragile over time, with confirmed failures under minimal effort; replacement with a more robust fitting is a prudent early upgrade. GFCI interior electrical outlets were not installed as original equipment, a gap that must be addressed by any owner planning to use shore power at modern marinas with current safety requirements. The bow thruster is almost mandatory; with the keel in the up position, docking dynamics change drastically, especially in a crosswind, and later Mk IV models incorporated joystick-controlled bow thruster hardware at the helm pedestal precisely for this reason. Cockpit access with a bimini or dodger installed is somewhat awkward, partially due to the North Sea-inspired cockpit design and represents an ongoing ergonomic trade-off for owners who rig a canvas package.
Refit Considerations
The transition from Mk I to Mk II hardware is the single most meaningful upgrade path for early hulls. The Humphreys-designed twin rudder system and deeper keel geometry address the ventilating-rudder tendency of the original single-rudder Mk I at a fundamental level. Owners of early hulls sourcing a retrofit should note that Southerly Yacht Services continues to offer spare parts even after the acquisition of Northshore by Discovery Yachts, providing a supply chain for swing-keel components, keel pennants, and hydraulic hardware that would otherwise require fabrication. Electrical systems aboard European-built examples favor European installation guidelines, meaning North American owners should budget for rewiring of shore-power circuits and panel upgrades to meet ABYC standards, including the GFCI outlets not fitted at the factory.
The Verdict
The Southerly 115 is a purposefully engineered answer to a real problem: how to cruise expansive shallow-water grounds without giving up seakeeping ability, interior comfort, or build quality. The Humphreys twin-rudder and deepened-keel refinement, locked in by the Mk II, makes the boat a legitimate offshore performer that also beaches gracefully. The construction standard is honest and durable, the interior is genuinely comfortable for two, and the hydraulic keel system is mechanically straightforward. Its shortcomings are knowable and manageable — rust maintenance on the iron keel, an aging shaft seal specification, a cockpit layout optimized for conditions rather than comfort — but none are disqualifying. This is a specialist's boat, built for sailors who actually intend to use the tide as a tool rather than a hazard.
Pros
- Hydraulic swing keel enables true shoal-draft operation with no performance penalty from a fixed-shallow keel
- Twin rudder system provides reliable directional control and lets the boat dry out on an even keel
- Solid below-waterline fiberglass construction; quality joinery and mechanical installations throughout
- Near-king-size aft owner's stateroom in a 37-foot center-cockpit layout
- Seldén rig with internal boom reefing and rigid vang supports shorthanded operation
- Spare parts pipeline maintained through Southerly Yacht Services post-acquisition
Cons
- Cast iron swing keel requires diligent rust management at every haulout
- Original shaft seal bronze hose barb is known to fail; replacement is a necessary early item
- No factory GFCI outlets — North American electrical compliance upgrades required
- Cockpit access is ergonomically compromised when a dodger or bimini is fitted
- Docking without a bow thruster is genuinely difficult with the keel raised in a crosswind
- Limited North American presence means parts, surveyors, and experienced yards are harder to locate than for domestic production cruisers
