How To Remove And Change A Boat Prop: A DIYers Guide

Sooner or later, your boat is going to need a new propeller. You can tow your boat to a mechanic to have this done, but many DIYers prefer to handle it independently. It's a fairly straightforward job that only takes 30 minutes if you have the right tools. Keep reading to learn how to change a boat prop.

What is a Boat Prop?

A boat propeller, often called a prop, is a fan-shaped device attached to the back of a boat. Made from metal or composite materials, it has several blades that spin around a central hub. This action turns the engine's power into thrust, moving the boat forward or backward and affecting its speed, handling, and fuel use.

Tools & Materials Needed:

• Prop wrench or socket set
• A small block of wood
• Sharp knife
• Flashlight
• Grease
• Rags
• Disposable gloves
• New boat propeller

Depending on the assembly of your propeller, you might also need a new cotter pin and a pair of needle nose pliers.

How to Change a Boat Prop

Step 1

Tilt the engine to a convenient height so you don't have to strain your back while working on the propeller. If your propeller assembly has a cotter pin, it will be on top of the prop nut. Use the needle nose pliers to pull the old cotter pin out and discard it.

Step 2

Use the block of wood to brace the prop against the cavitation plate. This will prevent the propeller from spinning as you remove the prop nut. Use your prop wrench or socket set to remove the prop nut, screwing counterclockwise. Remove both the nut and the washer that holds the propeller in place.

Step 3

Remember that when you install the new propeller, you will reassemble all the parts in reverse order. If you're new to this task, lay the parts out in a straight line so you don't forget the correct order. Once you remove the nut and washer, the propeller should slide straight off the shaft. If the prop appears stuck, you can give it a light tap with the wood block to try to loosen it. Don't hit it too hard, or you'll risk breaking something.

Step 4

At this point, your prop assembly may or may not have some additional parts on the shaft. These might include an aft adapter, a thrust washer, or a Delrin sleeve. Take these off before the next step, and place them in the proper order for reassembly.

Step 5

Once all the parts are off, wipe the shaft with a clean rag to remove any "gunk." This is also the perfect time to remove any fishing line wrapped around the prop shaft. Use the flashlight to see down into the assembly. Use a knife to cut the fishing line loose and get it all out. A fishing line can damage seals and bearings in your prop assembly if left too long.

Step 6

Apply some waterproof grease to the prop shaft. Your engine manufacturer will recommend brands to use for this. Just make sure it's a waterproof type of grease that does not contain graphite. Graphite can corrode outboard points, so you want to avoid using any product with it.

Step 7

Reassemble all the parts and the new propeller in reverse order. When you reattach the prop nut, use a prop wrench to tighten it to the proper torque. This may vary depending on your engine's manufacturer. You just don't want to over-tighten the nut when you reinstall it. If your assembly uses a cotter pin, installing a new one and bending the tails to lock the nut in place is the final step.

You're done!

Optimal Frequency for Propeller Maintenance

If you're a frequent boater, the fishing line will constantly threaten your prop assembly. It's a good idea to simply take the assembly apart, as described above, once a month to remove any fishing line that's caught on the shaft. 

You can also visually inspect the propeller at this time. Propellers can get dinged or notched at any time if you hit something in the water, and you might not even realize it. To ensure that your propeller enjoys a long life, have it professionally serviced once a year.

Top Reasons to Change Out or Remove a Boat Prop

Most boat propellers can last between 1,000 and 2,000 hours of use before they need to be replaced. This can obviously be shortened if you have an accident. Every propeller will eventually need to be replaced, although it's not uncommon to see a well-cared-for one that lasts a decade or more.

If you use your boat for multiple purposes, you may want to own different propellers for different situations. If you're going for a long cruise, a propeller with more pitch can increase your engine's fuel efficiency. If you go out to play on the lake for a weekend while towing water skiers or wakeboarders, a propeller with a low pitch might be more suitable.

Some boaters carry a spare prop and tools on board for "just in case" purposes. If an accident damages your propeller, you can swap it out without canceling your plans for a long weekend.

Another thing to note is that boat propellers are a tempting target for thieves. Many props are made from high-quality metals and fetch a reasonable resale price on the black market. A motivated thief with the right tools can swipe a prop in less than two minutes, and then you're out hundreds of dollars replacing it. When your boat is in storage or not in use, it's a good idea to remove the propeller and keep it safe until the following season.

Removing and replacing or maintaining a propeller is part of the boating lifestyle. If you learn how to do this task yourself, you can save time and money and keep your boat running smoothly for years!

At Gemlux, we understand the demands and needs of the boating industry because we are boaters. Check out our website for more boating tips and guides!

Note: Gemlux is not responsible for any actions taken related to fishing or boating, regardless of the advice given or not given on this website.