4 HP Mercury Outboard Boat Propellers Model 40 1973 - 1975
You Are Viewing Available Prop Pitches For:
- Manufacturer: Mercury
- Horsepower: 4 HP
- Years: 1973 - 1975
- Model: Model 40 Outboard
- Specs: Thru Hub Exhaust & 8 Tooth Spline
- Max RPM: 4500-5500 RPM
Please Choose A Propeller Pitch:
Where to Find Your Prop Pitch
around the inner hub.
Look on the outer hub of the prop near the blades or inside the hub.
Most props are stamped with a series of numbers.
Pitch is always the last number listed.
Example: 3 x 16 x 24.5R
3 - Number of Blades (occasionally displayed)
16 - Diameter
24.5 - Pitch
R - Direction of Rotation (R = Right/Standard, L = Left/Counter)
Prop Pitch & RPM's
For safety, and efficient performance, it is critical that your engine operates within the RPM range recommended by the manufacturer.
A change in the prop pitch will increase or decrease the engine RPM's and can be used to bring them into the recommended range. A 2" pitch increase (for example, from 21" to 23") will result in approximately a 300-400 RPM decrease and vice versa.
The correct prop allows the engine's RPM to run within the top end of the manufacturers recommendation.