Sierra Premium Lower Unit Gear Lube

An SAE 80W-90 API GL-5 gear lubricant for outboard and sterndrive lower units. GL-5 is the class that matters here: a lower unit runs hypoid gears under shock load in a housing that sits in water, so the additive package has to handle extreme pressure and it has to tolerate the odd drop of water without turning the gearcase into a rust bloom.

• Viscosity and class: SAE 80W-90, API GL-5. Direct substitute wherever an old hypoid 90 lubricant is specified.
• Fresh or salt water service.
• Protects gears, bearings and gearcase components and reduces friction.
• Color: amber, which makes it easy to read water contamination on the drain.
• Sizes: 10 oz tube or quart, each available individually or as a case of 12.

Pull the drain plug and look at what comes out before you refill. Milky lube means water is getting past a seal, and putting fresh lube into a leaking gearcase just buys you one more trip.