When it comes to propeller selection, there are many things to consider, not least of which is the propeller material itself. Most are made from some sort of metal or metal alloy, each with its own characteristic strengths and weaknesses. Most common among them are aluminum, stainless steel, bronze, Nibral – which is a nickel, aluminum and bronze alloy – and composite.
Aluminum is probably the most oft-used material for outboard and inboard/outboard propellers. Less expensive than the also-common stainless steel propeller, the aluminum prop has more flex. If you hit something while traveling at a high rate of speed, it's going to bend. This makes aluminum a fairly easy repair. The tradeoff, at least as far as an aluminum/stainless steel comparison, is that with aluminum, you lose some top-end speed.
Stainless steel is stronger and harder than aluminum. But it is also more costly to purchase and to repair. Hit something while traveling at a high rate of speed with this baby, and there's a chance something important may give way – the drivetrain, for instance, or, if you're luckier, a sheer pin. However, stainless steel provides greater top-end speeds than aluminum, and it is generally more durable than other prop materials.
Bronze propellers are found mostly on inboard boats – cruisers, yachts and some ski boats. They are more expensive initially than aluminum, but still reasonably affordable and repair easily. Note, however, that bronze propellers can be problematic in salt water, where they have a tendency to cause corrosion of aluminum surfaces. For this reason, and because there are other more durable materials available, bronze is becoming less popular as a propeller material.
Nibral – our nickel, aluminum and bronze alloy – is both extremely strong and durable. This is often the material of choice for boats in the 35-foot plus range and it is also found on small ski boats with inboard motors. Nibral is stronger than aluminum or bronze, and weaker than stainless – a circumstance that is reflected in its cost. It can be repaired relatively easily and its shape adjusted, or worked, as needed to ensure good reliability.
Composite propellers combine high tensile strength ceramic fibers and polymer resins to produce a tough, lightweight propeller at reasonable cost. Some models allow you to replace a damaged blade – as opposed to the entire prop – for real cost savings. Composite propellers are great for trolling motors, low horsepower motors and, because of their light weight, as a stow-aboard spare prop. They generally flex more than metal and metal alloy props, to the detriment of speed.
- Linda Hoff
