Mercury – Gear Lube Pump | Lower Unit Service Tool | 91-802891A1

Overview

This Mercury gear lube pump makes lower unit service a lot less messy and a whole lot more predictable. It threads right into a standard drain plug port, letting you push fresh lube straight from the bottle without juggling funnels or hoses. It’s a simple tool, but it saves time every season—especially when you’re doing back-to-back services on multiple motors. Most boaters end up keeping one in their kit because it’s dependable and doesn’t overthink the job.

Key Features

 • Threaded Pump Connection – Secures directly to a 3/8"-16 drain plug opening for steady, controlled pumping.
 • Metric Adapter Included – Adds a proper fit for gearcases using an M8 x 1.25 drain plug.
 • Bottle-Ready Design – Attaches to standard quart and liter bottles without extra adapters.
 • Direct Fill System – Pushes gear lube straight into the lower unit for clean, accurate service.
 • Service-Friendly Hose – Reduces drips and keeps the lube flow predictable during changes.

Engine & Boat Compatibility

 • Outboards and sterndrives with 3/8"-16 drain plug
 • Gearcases with M8 x 1.25 drain plug (with adapter)
 • All Mercury gear lube systems
 • Standard lower unit service setups

Performance & Practical Benefits

Using this pump feels clean and controlled, especially when you’re servicing a gearcase on a trailer or at the dock. There’s no rush to beat a dripping stream of oil or line up a funnel—everything stays threaded and steady. The pump gives a clear, natural feel as the gear lube moves through the case, making it easy to tell when pressure changes or the bottle is running low. Over time, it just becomes one of those tools you reach for without thinking.

Why Buy OEM

Mercury’s OEM service tools match the threads, depth, and flow expectations of their gearcases, so you’re not forcing a universal adapter into place. The materials hold up to repeated seasonal use, and the pump delivers consistent flow without odd leaks or weak points. It keeps communication clean between the bottle and the gearcase—nothing fancy, just reliable.

FAQ

Q1: How do I know I need a pump like this?
If you’re changing lower unit lube and fighting drips, mess, or slow filling, this tool makes the job smoother.

Q2: Does this pump require calibration or adjustment?
No adjustments—just thread it in and start pumping.

Q3: What if I service motors in saltwater?
Rinse the pump after use and it’ll hold up well season after season.

Q4: Any installation notes before pumping?
Thread the fitting in by hand first to avoid cross-threading, then attach the bottle.

Q5: What happens if the pump starts wearing out?
You’ll feel inconsistent pressure or see small leaks around the fitting, a sign it’s time to replace it.

• Supersessions
  91-802891K2, 91-8M0072135, 91-8M0072135