18" × 23" 螺旋桨规格
螺距比 1.28：1,000–4,000 RPM时的理论速度
Overview
A 18-inch diameter by 23-inch pitch propeller produces a pitch-to-diameter ratio of 1.28, which falls into the speed-biased, high-revving bracket. The diameter sets the disc area that converts engine torque into thrust, while the pitch sets the theoretical distance the propeller advances per revolution. At 2,500 RPM through a 1.5:1 gearbox this combination posts a theoretical no-slip speed of 31.5 knots; at the 4,000 RPM upper trace the same prop reaches 50.5 knots, with real-world slip pulling those numbers down by 10–20 percent depending on hull loading and bottom condition.
螺旋桨规格
| 直径 | 18" |
|---|---|
| 螺距 | 23" |
| 螺距比 | 1.28 |
各转速下的理论航速
| 转速 | 航速（滑移率0%） | 航速（滑移率15%） |
|---|---|---|
| 1,000 | 12.6 | 10.7 |
| 1,500 | 18.9 | 16.1 |
| 2,000 | 25.2 | 21.5 |
| 2,500 | 31.5 | 26.8 |
| 3,000 | 37.9 | 32.2 |
| 3,500 | 44.2 | 37.5 |
| 4,000 | 50.5 | 42.9 |
Typical applications
The 18"×23" size is most commonly fitted to offshore center consoles, cruisers, and 150–250 hp powered planing hulls, where the speed-biased, high-revving pitch profile matches the high-performance / racing performance window. Boats inside this class generally cruise between 31.5 and 50.5 knots on the speed chart above. High-RPM, high-pitch combinations are characteristic of light, planing hulls and performance fishing rigs. If your boat tops out far below the 50.5-knot theoretical figure, the propeller is over-pitched for your loaded weight and slip will climb toward the 15-percent column; if you over-rev past the engine's WOT range, the propeller is under-pitched and you should step up one or two inches of pitch.
Compared with adjacent sizes
Holding diameter at 18" and dropping pitch by two inches yields a lower top speed but quicker hole-shot and better load-carrying behaviour, which is why 18"×21" propellers are popular for heavy or family-loaded boats. Raising pitch by two inches to 18"×25" trades acceleration for roughly 2.7 knots of additional theoretical speed at the same RPM. Holding pitch at 23" and changing diameter shifts thrust area: a 17"×23" prop spins up easier on small engines, while 19"×23" needs a stiffer driveline but bites harder under load.
Sizing notes and assumptions
The speed table assumes a 1.5:1 gear reduction and the standard propulsion identity (pitch × RPM) ÷ (gear ratio × 1,215.2) to convert inches-per-minute into knots. Slip estimates of 0 percent (theoretical) and 15 percent (realistic cruising) bracket most clean-bottom planing hulls; expect higher slip on displacement vessels, fouled bottoms, or when towing. Always confirm propeller choice against the engine manufacturer's recommended WOT RPM window — landing inside the band protects the powerhead from lugging or over-revving and is the single biggest factor in long-term engine life.