When it comes to squeezing every ounce of performance from your 9.9–20HP Tohasu outboard, the choice of propeller is absolutely crucial. We manufacture high-quality aluminum propellers designed to fit a wide range of small horsepower engines—without claiming affiliation with Yamaha, Mercury, Suzuki, Volvo, or Honda. Our blades simply match their bolt patterns and splines, delivering reliable thrust and fuel efficiency whether you’re idling through a marsh or blasting across open water.

Why Propeller Specs Matter

Every dimension on a propeller—blade count, diameter, pitch, even the rotation direction—directly affects how your motor responds. A mismatched propeller can leave you lugging your engine at wide-open throttle or experiencing cavitation at speed. By understanding the nuances of blade geometry and pitch, you can:

• Optimize Acceleration: More blades typically improve hole shots but may reduce top-end speed.

• Balance Fuel Economy: A slightly smaller pitch can raise revs, burning more fuel; too large and your engine strains.

• Ensure Proper Handling: Right-hand rotation is industry standard, but make sure the hub spline count and bolt pattern suit your model.

Engine Compatibility

Our aluminum propellers fit the following 14-spline Tohasu outboards:

• HP Range: 9.9HP through 20HP

• 2-Stroke Models:

  • 9.9HP (1984 and newer)

  • 15HP (1985 and newer)

  • 18HP (1985 and newer)

• 4-Stroke Models:

  • 9.9HP (2000–2003)

  • 15HP (2000 and newer)

  • 18HP (2001–2003)

  • 20HP (2007 and newer)

• Classic 12HP: 1985–1988

Whether you’ve got an older 2-stroke plowing through weeds or a modern 4-stroke cruising lakes, our propellers bolt right on and deliver consistent performance.

Detailed Propeller Lineup

Below is a complete breakdown of our aluminum propellers, with every spec you need to make an informed decision.

Blade Count (B)

• Three-Blade: Lighter load, sharper acceleration, generally better for flat-water bass boats.

• Four-Blade: Extra grip in rougher water, improved handling under load, preferred for heavier boats or waterskiing.

Diameter (D)

Measured in inches, diameter influences how much water is “grabbed” per revolution. A larger diameter can boost thrust but may limit top speed if too large for your engine’s power band.

Pitch (P)

Stated in inches, pitch denotes how far the boat travels in one full rotation of the propeller.

• Lower Pitch (5–8″): Faster hole-shots, engine reaches optimum revs quickly.

• Higher Pitch (10–14″): Greater top-end speed but slower acceleration; watch rev limits.

Rotation (R)

All of the above models feature right-hand rotation, the industry standard for single-engine outboards. If you require counter-rotation, special orders may apply.

How to Choose the Right Aluminum Propeller

1. Check Your RPM
   Consult your engine manual for the recommended wide-open throttle (WOT) RPM range.

2. Match Diameter & Pitch
   Start with a prop that’s close to the factory spec. If you’re under-revving at WOT, drop 1″ of pitch; if you’re over-revving, add 1″.

3. Consider Your Boat’s Use

   • Fishing/Leisure: 3-blade, moderate pitch

   • Watersports/Heavy Loads: 4-blade, slightly lower pitch

4. Fine-Tune by Feel
   Nothing replaces on-water testing. Listen for lugging or overspeed; the right prop should put you in the sweet spot of the tachometer.

Final Thoughts

Investing in the proper aluminum propeller transforms how your Tohasu-powered boat behaves on the water. By carefully selecting the blade count, diameter, and pitch—and matching them to your engine’s RPM window—you’ll enjoy crisp acceleration, smooth handling, and the highest possible fuel efficiency. Remember, while we’re not the official propeller supplier for Yamaha or Mercury, our components slip right onto those popular 9.9–20HP outboards and perform as if they were designed in the factory! Choose wisely, test thoroughly, and get ready to rediscover your boat’s true potential.

Aluminum Propellers for 9.9–20HP Tohasu Outboard Boat Motor

When you’re navigating narrow backwaters or charging into open waves, every turn of your outboard counts. Our precision-cast aluminum propellers are engineered to fit 9.9–20HP Tohasu engines—offering unmatched thrust, lasting durability, and a price point that won’t sink your budget. Although many boaters run these blades on Yamaha, Mercury, Suzuki, Volvo and Honda outboards, we’re not affiliated with any OEM. Instead, we focus on crafting propellers that match the industry’s 14-spline hubs and bolt patterns, so you get seamless performance whether you’re chasing trophy bass or towing a tube.

Why Aluminum Propellers Shine

1. Lightweight Strength
   Aluminum combines a high strength-to-weight ratio with excellent fatigue resistance. You’ll feel quicker hole-shots without lugging down your motor.

2. Corrosion Resistance
   A robust anodized finish and marine-grade alloy fight saltwater pitting and galvanic corrosion—keeping blades sharper and smoother season after season.

3. Cost-Effective Replacement
   Unlike stainless steel, aluminum propellers deliver high performance at a fraction of the price, making it more economical to carry a spare or two aboard.

Unpacking Propeller Geometry

A propeller’s performance hinges on three primary specs:

• Blade Count (B): More blades equal more surface area in the water.

• Diameter (D): The circle the blades carve per rotation.

• Pitch (P): How far the boat moves forward in inches for each turn of the blades.

And don’t forget the rotation—all our models spin right-handed, the default for single-engine outboards.

Comprehensive Spec Table

Below is the full lineup of our 14-spline aluminum propellers for 9.9–20HP Tohasu outboards. Empty cells under OEM Number indicate no direct OEM match:

¹ Pitch range indicates available options when ordering; specify exact pitch.

Matching Your Engine

All models below share a 14-tooth spline hub. Here’s how they align with Tohasu outboards:

• 2-Stroke Engines

  • 9.9HP (1984–present)

  • 15HP (1985–present)

  • 18HP (1985–present)

• 4-Stroke Engines

  • 9.9HP (2000–2003)

  • 15HP (2000–present)

  • 18HP (2001–2003)

  • 20HP (2007–present)

• Classic 12HP

  • 1985–1988

Because we adhere to the standard 14-spline interface, these propellers also bolt onto the most popular Yamaha, Mercury, Suzuki, Volvo and Honda models of similar horsepower.

Selecting the Ideal Propeller

1. Consult Your Tachometer
   Before swapping props, note your wide-open throttle (WOT) RPM range.

2. Start with Stock Specs
   If your engine manual calls for a 9.25"×11" three-blade, that’s often the sweet spot.

3. Adjust for Use Case

   • Recreational/Wakeboarding: Four-blade, lower pitch (5–8”) for stronger pull and smooth acceleration.

   • Fishing/Leisure Cruising: Three-blade, moderate pitch (9–11”) for balanced speed and efficiency.

   • Heavy Loads: Drop one inch of pitch to keep RPMs in the optimal band when carrying passengers or gear.

4. Field-Test and Fine-Tune
   No spec chart replaces real-world feel. Try different pitches to maximize acceleration, top-end speed, and fuel economy in your typical boating conditions.

Installation and Care Tips

• Torque Bolts Correctly: Over- or under-tightening can warp the hub or loosen at speed.

• Inspect for Damage: Even small nicks or bends throw off your trim and fuel burn.

• Rinse After Saltwater Use: Flush with fresh water immediately to prevent corrosion.

Conclusion

Choosing the right aluminum propeller transforms your small outboard’s character: crisp throttle response, confident handling, and optimal fuel usage. By offering a full spectrum of blade counts, diameters, and pitches—and a perfect fit for Tohasu’s 14-spline hub—we provide the tools to tailor your boat’s performance. Dive into the specs above, match a prop to your engine and mission profile, and get ready to experience your vessel in a whole new light!