Do It Yourself: Common Boat Propeler Repair And Maintenance

A preventive maintenance plan for boat propellers with step by step instructions for fixing common problems and do-it-yourself solutions.

Many boat owners do not include the propeller in their preventive maintenance ritual, even though it is the final determining factor in boat performance, and the most common point of failure. There are a few propeller checks and minor repairs that you can perform yourself to avoid shortening your hard earned weekend at the lake.

First, you must remove the propeller from the shaft to inspect it and its components for wear or damage. To remove your propeller, you will need a variety of common hand tools: a pair of pliers, a flathead screwdriver, a rubber mallet, an appropriately sized deep well socket and ratchet, a small two-by-four, and a pair of leather gloves. Depending on the particular make, model, and year of the motor or outdrive, you might not need all the tools listed. If you find that you don't have a large enough socket for your prop nut, a 12 inch adjustable wrench should do the job.

Most manufacturers use a nut-retaining device to keep the nut from loosening during use. Generally, there are two types: a cotter pin, and a locking tab washer. If yours is a cotter pin, use your pliers to straighten it for removal. Lightly tap the pin ends with your hammer until you are able to grip the eye with your pliers. Tug firmly while rocking the pin and it should come out easily. If it won't come out, you may need to straighten it more.

If your nut retainer is a locking tab washer, you will need a flathead screwdriver. Insert the screwdriver under the downward-bent tabs and pry them upward until they will clear the notches in the locking washer. There may be two or more tabs locked, so be sure to check them all.

The propeller nut should be fully exposed and removable at this point. Put on your leather gloves for protection; prop blades can be extremely sharp. Wedge a short two-by-four between a prop blade and gear casing to prevent rotation while you use your socket and ratchet or adjustable wrench to remove the nut.

After you have removed the nut, slide any spacers off the prop shaft, and remove the propeller. In most cases, a thrust washer is located in front of the propeller. Remove it from the shaft as well. The thrust washer can easily become stuck on the shaft making it difficult to remove. If this is the case, gingerly tap it with a rubber mallet to free it from the shaft. In some instances, the thrust washer will adhere to the propeller. To separate, lightly pry with a flathead screwdriver.



With the prop and its related hardware out of the way, remove any fishing line, aquatic plant life, or other tangled material from the prop shaft. If allowed to accumulate, these tangles obstruct water and exhaust gas flow, and can cause costly friction damage to your propeller. To avoid seizing, apply a thin coat of waterproof grease to the splined (grooved) area of your shaft. Most late model prop shafts are splined, but if yours is not, apply a thin coat over the entire exposed shaft.

As you reinstall what you have removed in reverse, you will need to inspect for damage or excessive wear. The thrust washer should be perfectly round, fit snugly on the shaft, and be free of deep gouge marks. A damaged or worn washer would not properly space the propeller, and could potentially cause thousands of dollars in damage to your propeller and engine drive casing. If there are problems with the thrust washer, replace it with a new one.

Inspect your propeller for any cracks, nicks, or bent blades. If there are any cracks close to the center barrel of the prop, nicks larger than thumbnail size, or severely bent blades, you should take your propeller to an experienced and reputable repair station and have it repaired before you use it. If the damage is minimal, you can easily repair it yourself.

To repair slight bends or wobbles along the edge of a blade, lay a two-by-four on a solid, flat surface. While wearing your protective gloves, place the bent blade flat against the board. A majority of the blade edge should be touching the board, but the bent area will be raised. Hammer the bend, using your rubber mallet, with light to moderate force until the blade edge is uniform. Repeat as necessary with the remaining blades.

If you wish to repair the cracks or nicks yourself, and you don't have access to a welding machine, you will need a propane torch and a welding kit. You can find a welding kit, such as Alumiweld, at most hardware stores or on the Internet. Most kits come with an assortment of rod and a wire brush. This rod has a low melting point so you should be able to weld the nicks with a simple propane torch as long as it has a large tip. Follow the preparation and use instructions with both the propane torch and the welding rod. After sanding the welds smooth and flush with 80-grit sandpaper, repaint the exposed metal with factory touch up paint. Consult your local dealer for recommendations on the paint.

After you are satisfied with the condition of the propeller, reinstall it onto the shaft and properly seat it onto the thrust washer. If you have washers or spacers that mount behind the prop, inspect those for damage or wear, replace if needed, and reinstall on the prop shaft. If your engine has a locking tab system, place a new locking tab washer on the shaft and twist the nut until it is finger tight. If your engine uses a cotter pin, tighten the nut finger tight and install the keeper.

To avoid losing your propeller and most of its hardware, proper installation of the nut retainer is crucial. Tighten the nut with a torch wrench to the specification listed in your owner's manual. If you don't have an owner's manual, your local dealer should tell you the specification. If your engine uses the locking tab retainer, use your screwdriver to bend all the aligned tabs downward into the locking groove. If none align, tighten the nut until at least two tabs will align. If your engine uses the cotter pin retainer, push the pin into the hole as far as you are able. Use your pliers to bend both pins to a 90-degree angle opposite each other. Step back and admire your well maintained boat.

Incorporate these instructions into your normal preventive maintenance plan for your boat, and it will always be in good working order.

© High Speed Ventures 2011