Sierra Prop Shaft 18-2166, Replaces 44-66060 / 44-824110, Fits MR/ALPHA & #1 Units

The Sierra Prop Shaft 18-2166 is a machined replacement propeller shaft for MerCruiser sterndrive lower units, covering All #1 and MR/ALPHA units at serial number 2791957 and above, as well as 165 (6 cylinder) units at serial number 2763442 and above. The prop shaft transmits rotational power from the lower unit gearcase out to the propeller, and a worn, corroded, or bent shaft is a common cause of vibration, reduced thrust, or seal leakage at the propeller end of the drive. Machined to precise tolerances, the 18-2166 is built as a direct-fit alternative to the original equipment shaft, using the same mounting interface so no modification to the lower unit housing is needed during installation. This shaft carries Sierra part number 18-2166 and cross-references to multiple Mercury Marine and MerCruiser OEM numbers, so it can be matched to your old shaft or parts diagram regardless of which OEM number is stamped on it. Because a prop shaft carries continuous rotational load and sits at a water-exposed seal interface, replacing a worn or damaged shaft promptly helps prevent secondary wear to the gearcase bearings and seals. Before ordering, confirm your unit's serial number falls within the listed ranges to ensure correct fitment.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-2166
• Weight: 4.58 pounds
• Product Dimensions: 0.39 x 0.39 x 0.39 inches
• Exterior Finish: Machined
• UPC: 030999311702
• OEM Cross-Reference: 44-66060, 44-660603, 44-824110, 44-660602, 44-55857

Fitment

• All #1 and MR/ALPHA units, serial number 2791957 and above
• 165 (6 cylinder) units, serial number 2763442 and above

Replaces (OEM)

• 44-66060
• 44-660603
• 44-824110
• 44-660602
• 44-55857

Frequently Asked Questions

What does the Sierra 18-2166 prop shaft fit? The 18-2166 fits All #1 and MR/ALPHA units at serial number 2791957 and above, and also fits 165 (6 cylinder) units at serial number 2763442 and above. Check your lower unit's serial number against these ranges before ordering.

What OEM numbers does the Sierra 18-2166 replace? It replaces OEM numbers 44-66060, 44-660603, 44-824110, 44-660602, and 44-55857, so it is a direct match for any of these part numbers found on the original shaft or in a parts diagram.

How much does this prop shaft weigh? The Sierra Prop Shaft 18-2166 weighs 4.58 pounds.

Is the 18-2166 an OEM or aftermarket part? The 18-2166 is a Sierra-brand replacement part, sold under Sierra's own part number rather than the original Mercury Marine or MerCruiser part number, but it is built to cross-reference directly with those OEM numbers.

Will the 18-2166 fit a 165 (6 cylinder) unit? Yes, the 18-2166 prop shaft fits 165 (6 cylinder) units at serial number 2763442 and above.

What material or finish does the 18-2166 shaft have? The Sierra 18-2166 prop shaft has a machined exterior finish.

Does installing the 18-2166 require modifying the lower unit? No modification to the lower unit housing is needed; the 18-2166 uses the same mounting interface as the original shaft it replaces.

What are the symptoms of a worn or bad prop shaft? Vibration, reduced thrust, and seal leakage at the propeller end of the drive are common signs that a prop shaft such as the 18-2166 needs replacement.

What is the part number for this prop shaft? The Sierra part number for this prop shaft is 18-2166.

What are the dimensions of the 18-2166 prop shaft? Listed product dimensions for the 18-2166 are 0.39 x 0.39 x 0.39 inches.

Does the 18-2166 fit MR/ALPHA units? Yes, the 18-2166 fits All #1 and MR/ALPHA units at serial number 2791957 and above.