The Seafarer 31 Mki is moderately powered for comfortable coastal cruising, with acceptable motion comfort for coastal passages.
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 22.3′, the Seafarer 31 Mki tops out around 6.3 knots in displacement mode — after that, the bow wave outruns the hull and resistance climbs steeply.
1.34 × √22.3′ LWL = 6.3 kts
Performance Ratios
Racing handicap, sail-carrying power, stability and comfort — and what each one actually tells you about a day on the water.
SA / Displacement
15.8
Moderate sail power — a capable coastal cruiser, not overpowered.
Comfort Ratio
29.7
Acceptable coastal comfort — fine for weekends, notice the chop offshore.
Capsize Screening
1.72
Below the 2.0 offshore threshold — acceptable for ocean passages.
Pounds/Inch Immersion
705lbs
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
29.7
Acceptable coastal comfort — fine for weekends, notice the chop offshore.
Under 20 — Snappy, racing motion
20–30 — Acceptable coastal
30–40 — Good offshore comfort
Over 40 — Very comfortable offshore
Capsize Screening Formula
1.72
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 Seafarer 31 Mki sits on the PHRF handicap spectrum — lower numbers mean faster boats.
Cruiser/Racer 90–150
Cruiser 150–210
Heavy Cruiser 210–300
Niagara 31
162s/nm
Irwin 31
192s/nm
Hullmaster 31
204s/nm
Contest 31
219s/nm
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° |
2.4 |
3.1 |
3.4 |
3.6 |
| Close Reach60° |
2.9 |
3.7 |
4.2 |
4.3 |
| Beam Reach90° |
3.6 |
4.6 |
5.1 |
5.3 |
| Broad Reach120–135° |
3.3 |
4.2 |
4.7 |
4.9 |
| Run150–180° |
2.7 |
3.4 |
3.8 |
3.9 |
These are simplified estimates based on hull speed (6.3 kts),
SA/D (15.8), 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 Seafarer 31 Mki — 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 Seafarer 31 Mki.
|
Seafarer 31 Mki |
Contest 31 |
Hullmaster 31 |
Irwin 31 |
Niagara 31 |
Seafarer 31 Mki Yawl |
| Dimensions |
| LOA |
31.2 |
31.2 |
31.3 |
31.1 |
31.3 |
31.2 |
| LWL |
22.3 |
23.4 |
22.7 |
22.3 |
24.3 |
22.3 |
| Beam |
8.8 |
9.3 |
9.3 |
9.6 |
10.3 |
8.8 |
| Displacement |
8 |
10 |
10 |
9 |
8 |
8 |
| Ballast |
3 |
5 |
4 |
3 |
3 |
3 |
| Sail Area |
417 |
386 |
455 |
448 |
492 |
404 |
| Performance |
| PHRF |
— |
219 |
204 |
192 |
162 |
— |
| SA/Disp |
15.8 |
12.9 |
15.4 |
15.9 |
19.7 |
15.3 |
| Bal/Disp |
— |
53.5 |
42.0 |
39.6 |
44.4 |
38.3 |
| Comfort |
29.7 |
32.2 |
32.7 |
29.4 |
21.1 |
29.7 |
| Capsize |
1.72 |
1.71 |
1.70 |
1.81 |
2.05 |
1.72 |
| Hull Speed |
6.3 |
6.5 |
6.4 |
6.3 |
6.6 |
6.3 |