Sierra 18-0559 Outboard Prop Shaft Oil Seal, Replaces OMC 332585

The Sierra 18-0559 is an oil seal built for outboard prop shaft and driveshaft applications. It keeps water out and lubricant in around the rotating shaft, protecting the lower unit gearcase from water intrusion and preventing lubricant loss that can lead to premature gear and bearing wear. The seal is sized to a 0.357 inch outside diameter, a 0.285 inch shaft size, and a 0.940 inch width, so it seats precisely in the housing bore it is designed for and rides correctly against the shaft without leaking.

This part is a direct equivalent to OEM OMC 332585, giving boat owners and marine technicians a way to source the correct seal without going through OMC directly. It is a small, precise component, so correct orientation and a light coat of marine grease during installation help it seat fully and seal properly on the first try. Because it is a wear item exposed to constant water contact and shaft rotation, it is a common preventive-maintenance replacement during lower unit service, gearcase rebuilds, or whenever water is found in the gear lubricant.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-0559
• Outside Diameter: 0.357 inches
• Shaft Size: 0.285 inches
• Width: 0.940 inches
• Weight: 0.01 pounds
• UPC: 030999874603
• OEM Cross Reference: OMC 332585

Fitment

Designed for outboard prop shaft and driveshaft seal applications.

Replaces (OEM)

• OMC 332585

Frequently Asked Questions

What does the Sierra 18-0559 oil seal replace? The Sierra 18-0559 is a direct cross reference to OEM OMC 332585, so it installs as a like-for-like replacement for that part number.

What size is the Sierra 18-0559 oil seal? It measures 0.357 inches outside diameter, 0.285 inches shaft size, and 0.940 inches in width.

Is the Sierra 18-0559 an OEM part or an aftermarket equivalent? It is a Sierra-branded aftermarket seal manufactured as a direct equivalent to OEM OMC 332585, not an OMC-branded part.

What application is the 18-0559 seal used for? This oil seal is designed for outboard prop shaft and driveshaft sealing, keeping water out of the gearcase and lubricant in around the rotating shaft.

How much does the Sierra 18-0559 oil seal weigh? The seal weighs 0.01 pounds, consistent with its small, precise seal profile.

What is included when you order the 18-0559? Ordering the Sierra 18-0559 gets you a single oil seal sized to a 0.357 inch O.D., 0.285 inch shaft size, and 0.940 inch width; no gaskets or hardware are included.

Why would I need to replace this seal? If water shows up in the gearcase lubricant or the lower unit is being rebuilt, the prop shaft seal is a common wear item to replace, and the 18-0559 is sized for that job.

Does the Sierra 18-0559 come with an OEM number I can cross-reference? Yes, its OEM cross reference is OMC 332585, which can be used to confirm it is the correct seal for your application.

How is the Sierra 18-0559 installed? The seal should be pressed squarely into its housing bore with the correct orientation and a light coat of marine grease on the lip to help it seat fully against the 0.285 inch shaft without leaking.

What is the UPC for the Sierra 18-0559 oil seal? The UPC for this Sierra oil seal, part number 18-0559, is 030999874603.