Boat Propellers: Repairs & Replacements

Your boat’s propeller connects the engine to the water, just as tires connect your car to the road. Unlike tires, your propeller is not going to wear with use but it is prone to damage, which can range from a few nicks in the blade edges to catastrophic damage from a severe bottom strike. The soft propeller hub can also be damaged in a bottom strike, or just from age. Even minor damage can impact boat performance, so it’s important to take good care of your propeller.

Caring For Your Boat's Propeller

Complete regular inspections.
Repair or replace the prop when damaged or bent.
If needed, replace the rubber or plastic hub that sits between the propeller and the propshaft.
Always carry a spare propeller onboard—just like a spare tire.
When in doubt, call in the professionals for assistance.

Boat Maintenance Guide

Regular Inspection

Get in the habit of inspecting your propeller during the boating season. With the transmission in neutral you’ll be able to turn the prop (be safe: always remove the engine kill switch before inspecting the propeller). Inspect for bent blades or nicks in the leading edge. If you don’t see any obvious damage, carefully run your fingers along the leading edge of the prop blades and check for burring, which can occur if the prop is run through sand. You can remove these burrs yourself with a mill bastard file.

Boat Propeller Repair

If prop blades are bent or otherwise damaged, the prop should either be replaced or repaired. Obviously with those bent blades the prop is not going to function properly and boat performance will suffer, but the damaged prop is also likely now unbalanced, which can cause vibration at high speed which can lead to more problems.

A good propeller shop can restore a prop with pretty significant damage, often by welding new material onto the affected blades and then grinding and shaping the blades back to original geometry.

A typical repair to an aluminum prop will cost $100 to $150, but expect to pay $200 to $400 to repair a stainless steel prop. It may be more cost-effective to simply replace a damaged aluminum prop, but when a new stainless prop costs $400 to $700, the repair makes economic sense. Prop repair requires special skills, tools and experience, so most marine dealers have a relationship with a prop shop and send propellers out for service.

Any time you strike bottom hard enough to damage the prop, you should also have a dealer inspect the propeller shaft. If the shaft was also bent on impact it will need to be repaired or replaced.

Hub Damage

Most props have a rubber or plastic insert between the propeller and the propshaft. This insert is designed to give way on a hard prop strike to protect the gearcase from shock—it’s cheaper to replace the prop than the gearcase. If your boat does not move when you apply the throttle, or will only move slowly, you may have “spun the hub.”

A prop shop can usually replace a spun rubber hub. The plastic hub inserts used on many new props are simple to replace, and you can carry a spare and replace the plastic insert yourself on the water. The rubber hubs will also deteriorate over time and may need to be replaced even if you don’t strike bottom.

Always Carry a Spare

A spare prop is just like a spare tire—a replacement you can use in an emergency. If your prop is too badly damaged to get you home, replacing the prop is an alternative to getting towed back to shore. Many boaters buy a used prop of the correct size to carry as a spare. You can use an affordable aluminum prop as the back-up to a stainless prop. You’ll also need a propeller wrench to remove the prop nut, and should carry a spare nut, thrust washer and any other hardware required to replace your prop just in case you drop a part into the water. Practice changing the prop in the marina or with the boat on a trailer so you know the drill. Changing a prop at sea can be tricky if the water is rough; if that’s the case it may be safer to call for a tow.

Looking for more on maintenance and repairs? Read...

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