The hubs of propellers on outboards and sterndrives are designed to give way if the prop strikes an object to prevent damage to the rest of the drivetrain. However, hubs — particularly the old-style rubber hubs — can also wear out with time and heat. So if your prop is 10 years old or older, it is a good idea to have a prop shop check the hub and replace it (“rehub” it) with a fresh one if it thinks it is on the verge of giving way.
Errant fishing line — especially the newer braided line — can quickly melt and become a sharp-edged disc once it gets wrapped around a prop shaft; then it can slice into the prop-shaft seals. With inboards, carefully inspect the outside of the shaft seals and have the yard replace a seal if there is any indication of fishing-line damage.
On outboards and sterndrives, remove the propeller and hardware and check for fishing line. Remove any line you find and look for leakage of gear lube, which might have a milky hue if the seal has been leaking for any period of time. Even with no sign of leakage, drain the gear lube and have a shop pressure-check the gear case. If the lower unit does not meet its pressure specifications, have the seal replaced, and then refill the gear case with fresh lube.
Grease Before reinstalling the propeller, inspect the prop hardware and replace any worn components such as a cotter pin or keyway. Then apply a generous coat of fresh marine grease to the entire shaft and install the prop, tightening the prop nut to the engine builder’s specification. Greasing the prop shaft will make it easy next time to remove the wheel, particularly if the shaft and prop are dissimilar metals.
Quick Tip: Wedging a block of wood between a blade and the anti-ventilation plate or hull will keep the prop from turning while you remove or install the prop nut.