Retention washers include a washer body having a first side and a second side opposite the first side. The washer body has a perimeter having one or more lobes, and the retention washer further includes a multi-point star-shaped hole extending through the washer body from the first side to the second side. The retention washer is configured to maintain an installation torque of an installed nut when the retention washer is positioned such that the hole circumscribes the nut. Systems for retaining a propeller assembly on a shaft may include a nut installed on a bolt, and a retention washer positioned such that the hole of the retention washer circumscribes the nut, thereby limiting rotation of the nut with respect to the bolt and retaining the nut on the bolt. The system may include a circular array of nuts and bolts, each nut having a respective retention washer positioned thereon.