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Mariner 31
Designer: C. Oberly  ·  Builder: Far East Yachts  ·  First built: 1968
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About the Mariner 31

With limited documentation available, the Mariner 31 represents one of the more elusive designs in the 31-foot sailing category. This mid-sized sailboat appears to have been produced during an era when manufacturers were experimenting with various hull configurations and construction methods to appeal to the growing recreational sailing market. Based on its length and the typical design philosophy of boats bearing the "Mariner" name, this vessel likely embodies characteristics suited for coastal cruising and weekend sailing adventures. The 31-foot length suggests a boat designed to balance manageable size with reasonable interior accommodations, making it potentially attractive to couples or small families seeking their first serious cruising sailboat. Without extensive specification data, the Mariner 31's exact performance characteristics and design pedigree remain somewhat mysterious to modern boat researchers. This scarcity of information may reflect limited production numbers or a shorter manufacturing run. For prospective buyers encountering this model, thorough inspection becomes particularly important given the limited available technical documentation. Any examples still sailing today would represent survivors from what appears to have been a relatively uncommon design in the competitive 31-foot market segment.

Core Dimensions
LOA (Length Overall) 30.67 ft / 9.35 m
LWL (Waterline Length) 25.50 ft / 7.77 m
Beam 9.75 ft / 2.97 m
Max Draft 3.67 ft / 1.12 m
Displacement 11,500.00 lb / 5,216 kg
Ballast 5,000.00 lb / 2,268 kg
Sail Area (Reported) 482.00 ft² / 44.78 m²
Design & Construction
Hull Type Long Keel
Rigging Type Masthead Ketch
Construction FG with wood deck and cabin
Designer C. Oberly
Builder Far East Yachts
First Built 1968
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Performance Ratios
PHRF Rating PHRF (Performance Handicap Racing Fleet) is a national racing handicap measured in seconds per nautical mile. Lower values indicate faster boats. Ratings are sourced from US Sailing's national database (median across 60+ regional fleets).
Under 0 — Ultralight racer0–90 — Performance racer90–150 — Cruiser/racer150–210 — Typical cruiserOver 210 — Heavy/slow cruiser
231
SA/Displacement Sail Area to Displacement ratio measures how much sail power a boat has relative to its weight. Higher values mean more performance and speed.
Under 14 — Heavy cruiser, slow14–18 — Cruising sailboat18–22 — Cruiser/racerOver 22 — Performance racer
15.19
Comfort Ratio Ted Brewer's Comfort Ratio predicts how comfortable a boat will feel in offshore conditions. Higher values mean a steadier, more comfortable motion in a seaway.
Under 20 — Uncomfortably rough20–30 — Acceptable coastal30–40 — Good offshore comfortOver 40 — Very comfortable offshore
31.64
Capsize Screening Formula The USHS Capsize Screening Formula estimates offshore capsize risk. Lower is safer — values under 2.0 are considered acceptable for offshore sailing.
Under 2.0 — Safe for offshore2.0–2.2 — Borderline offshoreOver 2.2 — Coastal use recommended
1.73
Hull Speed Hull Speed is the theoretical maximum speed of a displacement hull, calculated from waterline length. Most cruising sailboats reach this speed in moderate conditions. 6.77
S# (Speed Number) The Speed Number (S#) is a quick performance index. Higher values indicate a faster, more powerful design relative to its size.
Under 3.0 — Slow cruiser3.0–5.0 — Average cruiser5.0–7.0 — Performance cruiserOver 7.0 — Racer
1.31
Pounds/Inch Immersion Pounds per Inch Immersion (PPI) tells you how much weight is needed to sink the boat one inch. Useful for calculating how additional gear and stores affect waterline. 888.36
Rig Dimensions
I (Foretriangle Height) 34.25
J (Foretriangle Base) 12.75
P (Mainsail Luff) 29.75
E (Mainsail Foot) 11.92
SA Fore 218.34
SA Main 177.31
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