Express Mach4 Propeller 13.5x15 – 4-Blade Stainless Steel, RH Rotation | 40–150hp (4.25" Gearcase)

Express Mach4 Propeller — 13.5 x 15, 4-Blade Stainless Steel, Right-Hand Rotation

The Express Mach4 is a premium 4-blade stainless steel propeller built on a Swept Cleaver design — delivering the hole shot, handling, and load-carrying advantages of a 4-blade without sacrificing top-end speed. Built from proprietary TP17™ stainless steel with performance-tuned exhaust vents and race-proven geometry, it’s engineered for outboards and sterndrives from 40 to 150hp with 4.25-inch gearcases.

Best Use Case

The Mach4 in 13.5 x 15 pitch is ideal for watersports boats, sterndrive applications, tri-toons, and bay boats running 40–150hp engines with 4.25" gearcases where acceleration, cornering, and load-carrying matter as much as top-end speed. The 15-pitch delivers strong bow lift and a fast hole shot — making it well-suited to boats that carry variable loads, tow riders, or need confident handling in choppy conditions. It’s also an excellent upgrade over older OEM stainless designs, and the tuned exhaust vents deliver best-in-class reversibility for docking in tight quarters.

Swept Cleaver Design — How It Works

The Mach4 uses a Swept Cleaver blade profile — a 4-blade design that maintains 3-blade top-end speed while delivering superior hole shot, handling, and rough-water stability. The swept blade geometry reduces drag at high speed while the 4-blade configuration provides more constant thrust and better stern lift than a 3-blade at the same pitch.

Key Features

• TP17™ Proprietary Stainless Steel — 20% higher chromium content than standard stainless for superior corrosion resistance and a higher-gloss finish. Nearly 250% stronger and 5x more durable than conventional stainless steel alloys.
• 4-Blade Swept Cleaver Design — Maintains 3-blade top-end speed while delivering superior hole shot, handling, and rough-water stability.
• Full Hull Lift — Raises the entire hull higher out of the water, reducing wetted surface and maintaining top speed under heavy loads where a 3-blade can lose up to 3 mph.
• Tuned Exhaust Vents — Optimized exhaust flow pathways improve hole shot performance and deliver best-in-class reversibility.
• Rough Water Stability — The 4-blade configuration smooths out chop and reduces porpoising, giving the helm a more planted, confident feel at speed.
• Broad Engine Compatibility — Fits Evinrude, Honda, Johnson, Mariner, Mercury, MerCruiser, Nissan, OMC, Parsun, Suzuki, Tohatsu, and Yamaha outboards and sterndrives.

Specifications

• Part Number: 31431530
• Diameter x Pitch: 13.5" x 15"
• Blades: 4
• Material: TP17™ Stainless Steel
• Rotation: Right-Hand (Standard)
• Gearcase: 4.25" (mid-large)
• Compatible Engine Range: 40–150hp outboards & sterndrives
• Hub System: 500-Series hub kit required (sold separately)

Parts Desk Insights

Hub kit required — not included. This propeller uses the 500-Series interchangeable hub system. Confirm your engine make, model, and year against the application chart to select the correct kit before ordering.

Note the gearcase size. This is the 4.25" gearcase version of the Mach4 — designed for 40–150hp mid-range outboards and sterndrives. If you’re running a 90–300+hp engine with a 4.75" gearcase, you need the larger-gearcase Mach4 series. Browse the Mach4 4.25" gearcase lineup by pitch:

• Express Mach4 13.25 x 17 — 4-Blade SS, RH (4.25" Gearcase)
• Express Mach4 13 x 19 — 4-Blade SS, RH (4.25" Gearcase)

Also available in the 3-blade Mach3 configuration for this gearcase: Express Mach3 13.75 x 15 — 3-Blade SS, RH. For the larger 4.75" gearcase Mach4 series, see the Express Mach4 15 x 15 — 4-Blade SS, RH.