What is the difference between Bronze and Nibral?


What is NiBrAl?

And how is it different from bronze?

In the realm of inboard propellers and ski wheels, we primarily see products made of Manganese Bronze or NiBrAl which is an alloy blend with nickel, bronze, and aluminum. While the two look very much alike, nibral is considered harder, stronger and more corrosion resistant. To get technical, Manganese Bronze Alloy has a tensile strength of 65,000 PSI, and yield strength of 25,000 PSI. Nibral has a tensile strength of 90,000 PSI, and a yield strength of 37,000.

In accordance with those features, nibral does generally cost more and take longer to work on in the machine or repair shop.

How can you tell the difference?

Some propeller brands work exclusively in Nibral including Acme and OJ, whos ski wheels we stock. Most of the time, a nibral propeller will be stamped somewhere on the hub indicating the metal type. It’s not always visible when a propeller is pulled off a boat and has growth or electrolysis, but once our prop-tech gets them all cleaned up, markings become visible. In some cases, companies who work exclusively with nibral do not stamp the material on the hub of the propeller, and we find out when our prop-tech gets his hands on the project.

Should I choose bronze or nibral?

Excellent question. Either material is suitable in many inboard applications. We generally recommend nibral specifically when a prop is considered “over square,” which is when the pitch is greater than the diameter. Some boaters also report greater longevity with nibral when they are running high horsepower motors, or logging a lot of hours with less extensive maintenance repair required. Cost may be another factor to consider. The purchase cost of a nibral inboard will be higher than bronze, as will repair work you may need done in the future. Sometimes the choice is made by availability, and others by preference.

Enjoy these photos of a recent Bronze Propeller Repair: