Design and Construction
The Mariner 31 hull is made of fiberglass, and the boat is built with a long keel and a full keel. Her displacement-length ratio of 310 places her among the "heavy cruisers," and only 27 percent of comparable sailboat designs are heavier heavy cruisers. The 43.48 percent ballast ratio is higher than 46 percent of all similar sailboat designs, giving her a stability foundation 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 tuck into shallow marinas while keeping the directional security of a full forefoot.
Rig and Handling
The Mariner 31 is built with a ketch rig, and her sail plan carries more rig than 50 percent of similar sailboats — enough to place her right at the average for the type spot on average. The standing and running gear follow period ketch conventions: mainsail, jib/genoa, and spinnaker halyards each run about 24 meters with 10 mm diameter, while sheets for jib, genoa, and mainsheet use 12 mm line at 9.4, 9.4, and 23.6 meters respectively. A spinnaker sheet of 20.8 meters, plus cunningham, kicking strap, and clew outhaul all at 10 mm, complete 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.
Accommodations
The Mariner 31 provides a 30.67-foot fiberglass hull with 38 gallons of gasoline in a single Universal Atomic 4 engine of 30 horsepower and 40 gallons of water capacity as her baseline platform.
The Verdict
The Mariner 31 is a straightforward heavy-cruiser ketch of the late-1960s school: solid fiberglass construction, full long keel, and a ballast ratio that leans toward stability over tenderness. She is not a light-air sprinter, but her 6.8-knot hull speed and heavy-cruiser displacement 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 peers heavier
- Ketch rig with average sail area for the class
Cons
- Gasoline Atomic 4 power rather than modern diesel
