Aluminum Propeller 9.9x13R for 20-25HP (High-Pitch for Light Boats)

This 9.9x13 aluminum propeller has a high pitch, designed to squeeze maximum speed out of ~20-25 HP outboards. If your boat is relatively light or has a fast-planing hull, this prop will allow the engine to convert excess RPM into velocity. For example, on a Yamaha 25 HP powering a 4-meter speedboat, the standard prop might let the engine rev too high without enough load – a 13″ pitch will harness that power more effectively by increasing distance traveled per revolution. The result is a higher top-end speed and lower fuel burn when cruising at a sustained brisk pace.

The construction is quality aluminum and engineered for smooth operation – even at higher speeds, the prop maintains stability and minimal vibration. This contributes to comfortable boat handling at fast throttle settings. With a diameter of 9.9″, the prop is balanced against the pitch to avoid overloading the engine. Installation is straightforward on the 13-spline shaft found on Yamaha/Parsun 20-25 HP and some Mercury/Mariner models in this range. The swap requires no special tuning – you use the same thrust washers and nuts from the original prop.

• Ideal Applications: Boats around 3.5 – 4.5 meters with 20-25 HP engines that carry minimal weight and aim for higher speeds. Example: a light fiberglass skiff or RIB with a 20 HP used for quick runs in calm waters – with this prop, the boat will achieve a greater top speed at wide open throttle.
• Recommended For: Situations where the engine with a lower-pitch prop hits maximum RPM too easily. By switching to a 13″ pitch, the WOT RPM drops, which spares the engine and improves efficiency. This is especially beneficial on long runs where fuel economy and optimal engine load are important.
• Tip: Observe if the boat still planes easily with the new prop. If you notice a slight delay in takeoff (due to the higher pitch), ensure the boat is kept light and not overburdened. This propeller shines under light load – for heavier conditions, it can be alternated with a 9.9x10 or 9.9x11 prop for stronger pulling power.
• Compatibility: The 13-spline hub makes it compatible with Yamaha & Selva 9.9-15 HP four-strokes and 20-25 HP two-stroke models (as well as the Parsun F25). It also fits certain Mercury/Mariner engines around 20 HP from older generations that use a Yamaha-based gearcase. This broad applicability makes the prop a great option to improve performance on various engines in this range.