How to Remove a Boat Propeller

How to Remove a Boat Propeller
The reasons for removing a boat propeller include damage to the prop, tangled fishing line and maintenance. Because it is one of the easier things a boater can do, you might want to try it even if you don't have mechanical experience beyond checking the oil in your car. The principle is about the same whether you have a small outboard or inboard.


Difficulty: Moderately Easy

Things You’ll Need:
  • Pliers Adjustable wrench Rubber mallet Screw driver Pencil Zip-lock bag Marine grease
  • Pliers
  • Adjustable wrench
  • Rubber mallet
  • Screw driver
  • Pencil
  • Zip-lock bag
  • Marine grease
Step 1
Situate your motor so the prop is in easy reach on a workbench or on a trailer out of the water with the prop in the up position. If an electric starter is part of the package, disengage the battery so the motor can't accidentally start.
Step 2
Locate the "king nut" behind the prop shaft. This is the retaining nut that keeps the prop from slipping off the prop shaft and has slots cut into the rear of the nut to hold a cotter key or retaining key. The cotter key is an easily bent, folded-over piece of metal that looks like a fat bobby pin. Straighten the cotter key and tap the end through the hole in the prop shaft and pull it out with your pliers.
Step 3
Loosen the prop shaft nut with your wrench sized to the king nut. Mark the shaft with a pencil to show how far the prop was fitted to the shaft for re-installation.
Step 4
Pull the prop off. It should come off easily, but sometimes corrosion or an over-zealous previous owner may have forced the prop too tightly onto the shaft. In that case, a light tap at the front of the prop with your mallet, working evenly around the circumference of the prop, should pop it loose. If the prop is really jammed on, a prop puller may be needed. It is similar to a universal wheel hub puller and available in a variety of forms at auto and marine supply stores. Better yet, if you know a boating friend who has one, borrow it. Although relatively inexpensive, it isn't something you are likely to use that often.
Step 5
Place all the parts in a zip-lock bag that stays with your motor and won't be lost. The cotter key can usually be reused, but even if it looks like it's been through too much wear, replacement is only pennies. When replacing the prop, put some marine grease onto the shaft so it won't be a chore the next time it needs removal. It isn't the torque of the prop on the shaft that holds it, it is the king nut and cotter key. Snug is good enough.

Tips & Warnings

Keep a spare cotter key, vise-grip wrench and prop in your boat in case your prop hits a rock miles from your launch point.

Article Written By Richard Nilsen

Richard Nilsen writes poetry, fiction, features and news stories in upstate New York. He was an emergency mental-health consultant for 20 years and directed a mentoring agency for a decade. Nilsen is a black-fly control technician in the Adirondack Park, where he enjoys hiking, biking and boating.

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