Specifiche Elica 15" × 13"

Overview

A 15-inch diameter by 13-inch pitch propeller produces a pitch-to-diameter ratio of 0.87, which falls into the balanced cruising 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 17.8 knots; at the 4,000 RPM upper trace the same prop reaches 28.5 knots, with real-world slip pulling those numbers down by 10–20 percent depending on hull loading and bottom condition.

Specifiche elica

Velocità teorica per giri

Typical applications

The 15"×13" size is most commonly fitted to family runabouts, walkarounds, and 75–150 hp center consoles, where the balanced cruising pitch profile matches the planing performance window. Boats inside this class generally cruise between 17.8 and 28.5 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 28.5-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 15" and dropping pitch by two inches yields a lower top speed but quicker hole-shot and better load-carrying behaviour, which is why 15"×11" propellers are popular for heavy or family-loaded boats. Raising pitch by two inches to 15"×15" trades acceleration for roughly 2.7 knots of additional theoretical speed at the same RPM. Holding pitch at 13" and changing diameter shifts thrust area: a 14"×13" prop spins up easier on small engines, while 16"×13" needs a stiffer driveline but bites harder under load.

• 15"×15"
• 14"×13"

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.