Prop Nut Torque

With the nice weather and the boating season in full swing in most parts of the United States, it is a good time to check the torque of the prop nut. This is part of the maintenance schedule and is
recommended to be done after every 20 hours of use. The fact that the nut is castellated and retained with a cotter pin makes people think that this is a set-and-forget fastener.

This often-overlooked fastener is even more important as motor power and boat size increase. A tremendous amount
of force is being applied to the prop when in use, even more so on boats with high transoms and surface-piercing
props. These forces can cause some movement of the prop. This can lead to some wear to the bushings that help to
retain the prop on the prop shaft. This wear can decrease the effective torque applied by the prop nut. As prop-nut torque decreases,
the prop’s movement increases, accelerating the wear. If the applied torque gets too low, the propeller can break the prop shaft when
under use. This is a very dangerous situation, particularly at the high speeds a modern bass boat is capable of.