During that six-year run, Gulfstar launched 172 hulls, making the 50 Kth the marque’s most popular sailboat. Period observers regarded it as the best boat the company ever built.
Design and Construction
The hull uses a straightforward solid-fiberglass laminate of mat and woven roving, although a few hulls may instead be balsa-cored. Rather than relying on molded liners for stiffness, Gulfstar tabbed full bulkheads and furniture components directly to the shell.
The deck is balsa-cored as standard, through-bolted to the hull, and glassed over from below. A long fin keel contains lead chunks embedded in a concrete slurry, so the ballast is encapsulated rather than bolted on. The full-length rudder skeg is bolted in place.
The Gulfstar 50 Kth displaces 35,000 pounds and carries 10,500 pounds of ballast. Beam is 13 feet 8 inches, and the waterline measures 39 feet 8 inches. The hull form is moderate and relatively narrow. Its 30 percent ballast-displacement ratio means the boat benefits from early reefing to stay upright in a moderate breeze according to this assessment.
All tankage sits beneath the floorboards. This lowers the center of gravity, softens the boat’s motion, and leaves the spaces beneath berths and settees available for storage.
Rig, Performance, and Handling
The sail plan isn’t especially large in either configuration: about 895 square feet as a sloop and 963 square feet as a ketch. Wide mast spreaders and chainplates set nearly outboard keep the sheeting angles open.
In a seaway, the Gulfstar 50 Kth is well mannered. Its forefoot bites, and the bilges are deep enough that the boat seldom slams in a chop. It also doesn’t gripe to weather. Most owners report that it won’t sail well to windward unless the apparent-wind angle is 45 degrees or greater.
The boat prefers moderate to heavy air. Once the wind passes 12 knots, it will readily make 7 knots or better under working sail. Below that, it needs a light-air spinnaker or mizzen staysail to maintain performance. Nominal hull speed is 9.3 knots.
Accommodations
The more popular interior grew out of the charter trade and provides three staterooms. Aft, the master suite has an en suite head and a separate shower arranged around an enormous U-shaped double berth. Forward, the V-berth fills in to form a double and shares a head with the saloon. A third cabin lies amidships to starboard, with two single berths and its own small head.
The L-shaped galley runs along the port side of the walk-through beneath the center cockpit. Its twin sinks sit close enough to the centerline to drain on either tack. In the saloon, a dinette is to port, with a settee and pilot berth to starboard.
In the two-stateroom version, the amidships cabin is replaced by a wraparound navigation station and additional engine space. Period reviews praised the teak joinery and generous volume. The boat can sleep up to eight.
Machinery and Tankage
Most boats left the factory with a 62-horsepower Perkins diesel. It is reliable but slightly underpowered when driving into a head sea. Gulfstar later offered an 85-horsepower Perkins, which drives the boat better. Several surviving examples have since been repowered with turbocharged Yanmar diesels.
Standard fuel capacity is 100 gallons, modest for a boat of this size. Because the fuel tank sits low, the engine’s fuel pump has to work hard. A day tank mounted higher in the boat and connected by a transfer link is a worthwhile upgrade.
Many boats were delivered with Onan generators. These have proved troublesome and are best replaced.
Known Issues
Hull blisters have appeared over the years. They’re usually cosmetic, but in some cases they’ve been associated with saturated cavities around the ballast.
The mainmast step is an iron plate located in the bilge over the keel, where it’s prone to corrosion. On ketch-rigged boats, the mizzen step can crush the deck core beneath it.
Leaks around deck fittings, hatches, and portlights are common. On some boats, the bronze stern tube surrounding the rudderstock has separated from the laminate and needs to be rebonded. Loose tabbing around bulkheads and subfloor structures has also been reported and requires re-tabbing.
Ownership and Refits
The Gulfstar 50 Kth’s recurring problems are well understood, and owners who have addressed them tend to be very satisfied. Refits may include addressing the mast steps, deck leaks, loose tabbing, stern-tube bonding, fuel delivery, and the original generator where fitted.
The Verdict
The Gulfstar 50 Kth is a thoughtfully laid-out large cruiser whose simple, robust structure and versatile accommodations have aged well. It’s a steady sea boat with a usable, though not expansive, sail plan. Its common defects are well understood and tractable.
The main ownership caveats are the modest fuel capacity and troublesome original Onan generators. Light-air performance also depends on carrying suitable sails.
Pros
- Proven hull, with 172 built and enduring owner satisfaction
- Practical charter-derived volume, with three- and two-stateroom layouts
- Low tank placement softens the motion and frees storage space
- Well mannered in a seaway and seldom slams in a chop
Cons
- Mainmast-step corrosion and possible deck-core crushing beneath the mizzen step
- Modest fuel capacity and a hard-working engine fuel pump
- Troublesome Onan generators; replacement is advised
- Modest sail area; light-air performance requires a spinnaker or mizzen staysail
