Whether you're replacing a propeller on your Mercury or removing it to take it to the prop shop for a tune up, removing the propeller on a Mercury Marine outboard is unlike propeller removal on other outboards. While other outboards have a hole drilled through their propeller shaft, a matching hole in the propeller, and a pin can inserted through both, Mercury Marine's propellers don't. A special washer does the job without weakening either shaft or propeller.
Remove the battery cables from your boat's battery. Disconnect the spark-plug wires from all plugs. Remove the keys from the ignition switch and place them in your pocket. Place a piece of duct tape over the ignition switch, to prevent anyone from accidentally attempting to start the motor.
"Block" the propeller in place by inserting a piece of scrap lumber between the propeller blades and under the fin of the motor's lower unit, located just above the propeller. This block will hold the propeller steady as you remove the propeller nut.
Bend each of the three tabs on the propeller retaining washer up and away from the propeller nut with a pair of pliers. This washer is on the propeller shaft, behind the propeller nut. The three tabs are bent over the top of the propeller nut and down into grooves on the nut to prevent it from working its ways loose during normal operation, causing you to "spin off" a propeller.
Turn the propeller nut--the big nut on the end of the propeller shaft--counterclockwise with an adjustable wrench to remove it. Once the nut is removed, the propeller-nut retaining washer will slide off and you can slide the propeller from the propeller shaft.
Items you will need
- Duct tape
- Scrap lumber
- Adjustable wrench
- Inspect the propeller and nut and propeller-nut retaining washer for damage and replace them if necessary.
- If you operate your boat in salt water, salt and corrosion may foul the threads on the propeller shaft. If removing the nut and washer proves difficult, spray the nut, the propeller-retaining washer and the propeller shaft with a moisture-excluding spray lubricant and wait half an hour before continuing.
- If you're replacing your propeller with a different style of propeller, remove all washers, fastenings, thrust rings and assorted paraphernalia from the propeller shaft. The new propeller has its out thrust rings, washers and fastenings and these should be used, rather than those already present.
- Do not reuse a damaged propeller nut or propeller-nut retaining washer.
- Don't make yourself a statistic. Never work on an outboard without ensuring it cannot start. Propeller strike injuries, even those where the motor tries to start but doesn't run, cause serious injuries and even fatalities among boaters every year.
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