A Comparison of Commonly Used Propeller Materials

The most common boat propellers today are made of composite-plastic, aluminum and stainless steel. Here is a quick guide their physical properties, relative costs, maintenance, ideal usage and how they can affect boating performance.

Composite / Plastic

  • Material Properties: Solid material that is made when two or more substances are combined physically to create a new material that is superior to both of those original materials in a specific application.
  • Price: Cheapest of the three.
  • Upkeep: May not be repaired, some manufacturers will provide replacement blades.
  • Strength: Lightweight, more prone to bending under loads and blades are made thicker to compensate. There is reasonable impact resistance, blade flex is common and there may be inability accept cupping due to the relative weakness of the blades.
  • Durability: Almost similar to aluminum, less than stainless steel.
  • Ideal Usage: Emergency purposes, spares, smaller engines, low-horsepower gasoline motors or electric trolling motors.
  • Saltwater/Freshwater Usage: Both.
  • Size: Most manufacturers make up to 23 inches, 3-4 blades, round ear and low rake.
  • Additional Information: Composite / Plastic props are corrosion resistant.

Aluminum

  • Material Properties: Made of alloys of other metals.
  • Price: Low price, slightly higher than composite / plastic propellers, lower than stainless steel.
  • Upkeep: The material is relatively soft and can be repaired at reasonable prices. Nicks and dings can be repaired but the coating on the propeller should be touched up to prevent corrosion.
  • Strength: Lightweight material, strong enough to reduce blade flex and has the ability to accept some amount of cupping.
  • Durability: Average durability. A well designed propeller will perform just as well as an average stainless steel propeller.
  • Ideal Usage: Can be for low or high horsepower applications, are widely available in a range of sizes for all types of applications making it the most popular choice of material.
  • Saltwater/Freshwater Usage: Recommended for fresh water usage only as aluminum will corrode much quicker in salt water.
  • Size: Most manufacturers make up to 23 inches, 3-4 blades, round ear, moderate pitch and low rake.
  • Additional Information: Most popular type of propeller.

Stainless Steel

  • Material Properties: Steel alloy with a minimum of 10.5-11% chromium content by mass.
  • Price: Much more expensive than the aluminum or composite / plastic.
  • Upkeep: Can be easily repaired, at a higher cost.
  • Strength: Very strong and efficient as it has stiffer, thinner blades that reduces resistance in water and almost eliminates flex. The blades are strong enough to accept significant cupping.
  • Durability: Longest lasting. These blades can withstand small rocks, sand and various loose objects in water.
  • Ideal Usage: Very versatile, but ideal for heavy or high speed applications, for improving acceleration and top speeds, increase trimming or holding ability.
  • Saltwater/Freshwater Usage: Both.
  • Size: Most manufacturers make around 29 inches and up, 4-5 blades, usually a round ear, adequate rake and large cup size.
  • Additional Information: There is minimal give, which means that the lower unit of a vessel can become damaged if an object hits it hard enough rather than damaging the blades. The heaviness of the blades can damage gears if the motor set too high.
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