Allied Seawind Mk II Ketch Sailboat Review, Specs, and Listings

Design Brief & Intent

The Allied Seawind Mk II was conceived as a premium, heavily built cruising yacht designed to cross oceans in comfort and safety. Gillmer met this brief by significantly scaling up the dimensions of the design. While its overall length of 31.58 feet was only a foot longer than the original model, its beam of 10 feet 5 inches and displacement of 14,900 pounds yielded a vessel with dramatically more interior volume and carrying capacity. It was designed to compete with the robust offshore cruisers of the era, such as the Southern Cross 31, and stood out for its exceptional construction standards.

Built to meet or exceed Lloyd's AAA requirements, the Seawind Mk II features a solid, hand-laid fiberglass hull. The deck and cabin trunk are balsa-cored to manage weight and prevent condensation, though high-load areas—particularly the cabin top under the deck-stepped mast—are cored with solid, filled epoxy to withstand extreme compression. One of the most remarkable aspects of the construction is the hull-to-deck joint. Both the hull and deck were molded with outward-turning flanges. Allied workers sandwiched a flat teak batten between these flanges using a thick bed of 3M 5200 adhesive, through-bolting the entire assembly vertically with stainless steel bolts. Once cured, the joint was glassed over heavily on the inside, and a heavy-duty extruded aluminum rub rail was secured horizontally on the outside. This labor-intensive joint is virtually indestructible and highly resistant to the leaks that plague other vessels of this vintage.

The interior of the Mk II reflects a major step forward in finish quality for Allied Yachts. Earlier models had been criticized for their heavy use of woodgrain Formica and sterile fiberglass modules, but the Seawind Mk II was finished with warm, hand-crafted teak joinery, structural bulkheads securely glassed to the hull, and an abundance of solid handholds necessary for moving about in a seaway. The layout provides a comfortable V-berth forward, an enclosed head with a vanity, a main salon with a folding table and pull-out settees, a dedicated navigation station, and an L-shaped galley aft, providing excellent headroom of 6 feet 2 inches 7.

While the ketch rig was the standard and by far the most popular configuration for the 130 hulls built during the production run, Allied did offer alternative sail plans. A total of eleven cutter rigs and five sloop rigs were constructed. The standard masthead ketch rig divides the sail area across a mainmast and a smaller mizzen mast stepped forward of the helm. This setup allows single-handed or short-handed crews to easily balance the boat under "jib and jigger" (headsail and mizzen) during heavy weather, keeping the boat stable and controllable without the need to struggle with reefing a large mainsail. However, the cutter and sloop rigs are highly sought after by purists because they eliminate the clutter of a mizzen mast and its associated rigging in the middle of the cockpit, which can restrict the helmsman’s movement and forward vision.

In terms of auxiliary power, the vast majority of Mk II hulls were delivered with a lightweight, four-cylinder 27-horsepower Westerbeke diesel. This engine provides more than enough torque to push the heavy hull through a headwind. Very early hulls were occasionally delivered with a Palmer P-60 gasoline engine, and some records indicate a few hulls left the factory with alternative small engines like a Bukh diesel or a 27-horsepower Vire engine. Over the decades, many owners have repowered their vessels, with three-cylinder Yanmar or Beta Marine diesels being the most popular modern replacements 9. All variations of the Seawind Mk II retain a uniform, moderate draft of 4 feet 6 inches, making it a perfect shoal-draft option for cruising the Bahamas and the Florida Keys while still preserving the tracking capabilities needed for offshore work.

Sailing Performance & Handling

The sailing characteristics of the Allied Seawind Mk II are defined by its traditional, heavy-displacement hull form. With a displacement-to-length ratio of 401.16, the boat is classified as an ultra-heavy displacement cruiser. It does not accelerate quickly in light breezes and can feel somewhat sluggish in winds under eight knots, a reality confirmed by its conservative sail area-to-displacement ratio of 14.66. In light air, keeping the boat moving requires a large genoa or an asymmetrical cruising spinnaker.

However, once the breeze builds, the Mk II comes into its own. This is a stiff, exceptionally stable boat that carries its momentum through chop without hobby-horsing or pounding. The ballast-to-displacement ratio of 36.24 percent, combined with a full keel and a cutaway forefoot, gives the boat excellent tracking and directional stability, allowing it to hold a course with minimal helm correction.

With a capsize screening formula of 1.69, the Seawind Mk II is incredibly safe and highly resistant to roll-over in extreme sea states. Its comfort ratio of 37.15 indicates a slow, gentle, and highly predictable motion in heavy weather. This soft motion reduces crew fatigue on multi-day passages, making it a favorite for long offshore cruises. At the helm, the rack-and-pinion wheel steering provides a solid, direct, and reliable mechanical connection 6. Under power, the full keel means the boat tracks beautifully forward, but reversing in tight marinas requires careful planning, as the boat will back up in its own predictable direction regardless of rudder input until water is flowing cleanly over the blade.

Known Issues & Triage

While the Seawind Mk II is built like an armored vault, decades of use have highlighted several specific, documented areas that demand careful inspection and maintenance. The most critical structural concern is the mast compression post support. The mainmast is stepped on deck, supported below by a massive oak compression frame that curves around the head doorway and anchors to the top of the ballast keel. Bilge water, condensation, or leaks from the head can pool around the base of this wooden frame. Over time, this standing water can cause the oak base to rot, leading to a slight sagging of the deck under the mast step. Triage requires stepping the mast, cutting away the compromised timber at the base of the frame, and fabricating a rot-proof riser out of teak, G10, or stainless steel that is thoroughly epoxied and glassed to the keel.

Another common headache for owners is the fuel tank 1. Allied installed a welded aluminum fuel tank deep in the bilge, often wrapping it in expanding foam. These tanks lacked inspection ports. Over forty years, trapped bilge moisture can lead to crevice corrosion on the exterior of the aluminum, eventually causing fuel leaks. Because the tank is located under the cabin sole, extraction is highly labor-intensive, usually requiring the removal of the engine or the cutting away of sections of the fiberglass cabin sole.

Additionally, while the deck-to-hull joint is incredibly strong, the sealant can dry out, and the screws holding the heavy aluminum rub rail can become paths for minor water leaks 4. Re-bedding the rub rail is a tedious but necessary task to keep the interior dry. Finally, like all boats of this era, the balsa-cored decks must be thoroughly surveyed with a moisture meter, particularly around the chainplates, stanchions, and deck hatches where deck hardware may have been improperly re-bedded over the years.

Modernization & Upgrades

Modern owners preparing the Seawind Mk II for long-term cruising prioritize power management, mechanical reliability, and plumbing upgrades. To maximize space and reduce weight, many owners have upgraded their electrical systems to lithium iron phosphate (LiFePO4) batteries. This allows them to run high-draw equipment like refrigeration, watermakers, and modern electronics packages without the need to carry a heavy generator.

Swapping out the original, bulky Westerbeke diesel for a modern Yanmar 3YM30 or Beta Marine 30 is the most common mechanical upgrade 9. These modern engines are significantly lighter, more fuel-efficient, and physically smaller, which opens up valuable space in the cramped engine compartment, making routine maintenance vastly easier.

For blue-water voyaging, water capacity is often a limiting factor. Some owners choose to bypass the original under-sole water tanks and build custom integral fiberglass tanks lined with food-grade epoxy, which can double the boat's fresh water capacity. Other common upgrades include converting the original standing rigging to heavier wire or synthetic line, installing modern roller-furling systems for the headsails, and mounting a windvane autopilot on the transom to handle the steering on long, off-the-wind ocean passages.

The Verdict

The Allied Seawind Mk II Ketch is an exceptional example of a classic, overbuilt American pocket cruiser. It is not a boat designed for blistering racing speeds or modern marina dock-side entertaining. Instead, it is a safe, stout, and highly reliable voyaging yacht meant to keep its crew secure in the worst offshore conditions. For a couple or solo sailor looking for a true blue-water boat on a modest budget, its structural integrity and gentle motion make it one of the finest options on the used market.

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