The Mariner 31 is moderately powered for comfortable coastal cruising, with a steady, comfortable ride offshore.
Hull Speed
The theoretical displacement-mode speed limit — determined by waterline length, not engine or sail power.
A displacement hull pushes a bow wave whose speed is limited by the waterline length.
With a waterline of 25.5′, the Mariner 31 tops out around 6.8 knots in displacement mode — after that, the bow wave outruns the hull and resistance climbs steeply.
1.34 × √25.5′ LWL = 6.8 kts
Performance Ratios
Racing handicap, sail-carrying power, stability and comfort — and what each one actually tells you about a day on the water.
PHRF Rating
231s/nm
Heavy or slow cruiser — all about the journey, not the elapsed time.
SA / Displacement
15.2
Moderate sail power — a capable coastal cruiser, not overpowered.
Comfort Ratio
31.6
Good offshore comfort — steady enough for multi-day passages.
Capsize Screening
1.73
Below the 2.0 offshore threshold — acceptable for ocean passages.
Pounds/Inch Immersion
888lbs
Weight needed to sink the hull one inch — loading sensitivity.
Motion & Offshore Suitability
Two ratios that matter most when you're planning passages — how the boat feels in a seaway, and whether the hull geometry is suitable for open ocean.
Comfort Ratio
31.6
Good offshore comfort — steady enough for multi-day passages.
Under 20 — Snappy, racing motion
20–30 — Acceptable coastal
30–40 — Good offshore comfort
Over 40 — Very comfortable offshore
Capsize Screening Formula
1.73
Below the 2.0 offshore threshold — acceptable for ocean passages.
Under 2.0 — Acceptable for offshore
Over 2.0 — Coastal / protected waters
PHRF Fleet Position
Where the Mariner 31 sits on the PHRF handicap spectrum — lower numbers mean faster boats.
Cruiser/Racer 90–150
Cruiser 150–210
Heavy Cruiser 210–300
Dufour 31
168s/nm
Nicholson 31
194s/nm
Monsun 31
204s/nm
Mariner 31
231s/nm
Heavy or slow cruiser — all about the journey, not the elapsed time.
Estimated Speed by Wind
Rough boat speed estimates at different true wind speeds and points of sail — derived from hull speed, SA/D, and displacement, not measured polars.
| Point of Sail |
6 kts TWS |
10 kts TWS |
15 kts TWS |
20 kts TWS |
| Close-hauled40–50° |
2.6 |
3.2 |
3.6 |
3.8 |
| Close Reach60° |
3.1 |
3.9 |
4.4 |
4.6 |
| Beam Reach90° |
3.8 |
4.8 |
5.4 |
5.6 |
| Broad Reach120–135° |
3.5 |
4.4 |
4.9 |
5.2 |
| Run150–180° |
2.8 |
3.5 |
4.0 |
4.1 |
These are simplified estimates based on hull speed (6.8 kts),
SA/D (15.2), and empirical efficiency curves — not instrument-measured
polars. Real-world speed varies with sea state, bottom condition, sail trim, and current.
Speeds in gold approach hull speed;
bold gold means near or at hull speed.
Wind Range & Comfort Envelope
Estimated wind ranges for comfortable sailing on the Mariner 31 — based on sail area, ballast, and displacement characteristics.
Ghost
Sweet Spot
Reef
Heavy
0–7 kts
7–20 kts
20–28 kts
28+ kts
Ghosting
0–7 kts
Light air, motor-sailing likely. Need patience and a light genoa.
Sweet Spot
7–20 kts
Comfortable under full sail. Best speed-to-comfort ratio.
Time to Reef
20–28 kts
Time to shorten sail. Reef the main, swap to a working jib.
Heavy Weather
28+ kts
Storm conditions. Storm jib or bare poles. Seek shelter if coastal.
How It Compares
Side-by-side with the boats most often cross-shopped against the Mariner 31.
|
Mariner 31 |
Chance 30 30 Allied |
Commander 31 Bianca |
Dufour 31 |
Monsun 31 |
Nicholson 31 |
| Dimensions |
| LOA |
30.7 |
30.6 |
30.7 |
30.8 |
30.8 |
30.5 |
| LWL |
25.5 |
25.0 |
22.0 |
23.0 |
24.7 |
24.2 |
| Beam |
9.8 |
10.0 |
8.8 |
10.5 |
9.4 |
10.2 |
| Displacement |
11 |
11 |
7 |
9 |
9 |
13 |
| Ballast |
5 |
6 |
3 |
3 |
4 |
4 |
| Sail Area |
482 |
483 |
334 |
395 |
414 |
484 |
| Performance |
| PHRF |
231 |
— |
— |
168 |
204 |
194 |
| SA/Disp |
15.2 |
15.5 |
13.7 |
14.0 |
15.1 |
14.1 |
| Bal/Disp |
— |
58.0 |
45.7 |
38.5 |
45.4 |
— |
| Comfort |
31.6 |
30.2 |
26.6 |
25.5 |
27.2 |
35.0 |
| Capsize |
1.73 |
1.79 |
1.79 |
1.98 |
1.80 |
1.74 |
| Hull Speed |
6.8 |
6.7 |
6.3 |
6.4 |
6.7 |
6.6 |