Hull Speed
The theoretical displacement-mode speed limit — determined by waterline length, not engine or sail power.
4.8 kts
A displacement hull pushes a bow wave whose speed is limited by the waterline length.
With a waterline of 13.0′, the Mercury 18 tops out around 4.8 knots in displacement mode — after that, the bow wave outruns the hull and resistance climbs steeply.
1.34 × √13.0′ LWL = 4.8 kts
Performance Ratios
Racing handicap, sail-carrying power, stability and comfort — and what each one actually tells you about a day on the water.
Ballast / Displacement
57.7%
Race-oriented ballast ratio — very stiff and powerful.
Displacement / Length
224
Moderate — a good balance of speed and load-carrying ability.
Hull Speed
4.8kts
Pounds/Inch Immersion
1lbs
Weight needed to sink the hull one inch — loading sensitivity.
How It Compares
Side-by-side with the boats most often cross-shopped against the Mercury 18.
| Mercury 18 | Cape Cod Knockabout | Duxbury Duck | Hampton One Design | Interlake | Rhodes 18 | |
|---|---|---|---|---|---|---|
| Dimensions | ||||||
| LOA | 18.0 | 18.0 | 18.0 | 18.0 | 18.0 | 18.0 |
| LWL | 13.0 | 15.5 | 15.1 | 14.0 | — | 17.0 |
| Beam | 5.3 | 6.0 | 6.3 | 5.8 | 6.3 | 6.3 |
| Displacement | 1 | 650 | 700 | 755 | 650 | 1 |
| Ballast | 635 | — | — | — | — | — |
| Sail Area | — | 165 | 342 | 175 | 175 | 162 |
| Performance | ||||||
| SA/Disp | — | 35.2 | 69.5 | 33.8 | 37.4 | 25.1 |
| Bal/Disp | 57.7 | — | — | — | — | — |
| Comfort | — | 5.7 | 5.8 | 7.4 | 5.4 | 8.2 |
| Capsize | — | 2.77 | 2.85 | 2.55 | 2.89 | 2.46 |
| Hull Speed | — | 5.3 | 5.2 | 5.0 | 5.2 | 5.5 |