Design and Construction
The Mariner 31 has a 30.67-foot fiberglass hull, a long keel, and a full keel. Her displacement-length ratio of 310 puts her among the “heavy cruisers”; only 27 percent of comparable sailboat designs are heavier.
Her 43.48 percent ballast ratio is higher than that of 46 percent of similar sailboat designs, providing a foundation for stability that suits offshore work. With a beam of 9.75 feet and a draft of 3.67 feet—rising to about 3.97 feet under load—she draws little enough to fit into shallow marinas while retaining the directional security of a full forefoot.
Rig and Handling
The Mariner 31 carries a ketch rig. Her sail plan has more rig than 50 percent of similar sailboats—enough to place her right at the average for the type.
The standing and running gear follow period ketch conventions. The mainsail, jib/genoa, and spinnaker halyards are each about 24 meters long and 10 mm in diameter. The jib, genoa, and mainsheets use 12 mm line in lengths of 9.4, 9.4, and 23.6 meters, respectively. A 20.8-meter spinnaker sheet, along with a cunningham, kicking strap, and clew outhaul—all using 10 mm line—completes the inventory a buyer or owner would expect to maintain.
The theoretical maximum hull speed is 6.8 knots, consistent with her displacement and waterline.
Machinery and Tankage
Auxiliary power comes from a single 30-horsepower Universal Atomic 4 gasoline engine. The Mariner 31 carries 38 gallons of gasoline and 40 gallons of water.
Verdict
The Mariner 31 is a straightforward heavy-cruiser ketch of the late-1960s school, with solid fiberglass construction, a long full keel, and a ballast ratio that favors stability over tenderness. She isn’t a light-air sprinter. Instead, her heavy-cruiser displacement and 6.8-knot hull speed mark her as a steady voyager for sheltered and moderate waters rather than a performance racer.
Pros
- Long full keel and 43 percent ballast ratio for directional stability
- Heavy-cruiser displacement, with only 27 percent of comparable designs being heavier
- Ketch rig with average sail area for the class
Cons
- Gasoline-powered Atomic 4 rather than a modern diesel
