Complete Guide to Marine Gear Lube for Outboards, Sterndrives, and Inboards

Keep your Boat's Lower Unit Protected with Proper Gear Lube

Maintaining your boat's lower unit with fresh gear lube is one of the most important steps in ensuring reliable performance and longevity. Gear lube reduces friction, prevents corrosion, and protects crtitical components such as gears, bearings, and seals from wear and water intrusion. Proper gear lube maintenance helps your engine, whether its and outboard, sterndrive, or inboard, operate smoothly and efficiently season after season.

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Why Gear Lube Matters

The lower unit, whether on an outboard or a sterndrive/inboard is exposed to constant pressure, water, and contaminants. Over time, gear lube can break down or become contaminated, reducing its effectiveness and increasing the risk of:

  • Corrosion from water or moisture
  • Premature wear on gears and bearings
  • Damage from debris or heavy loads

Regular gear lube changes ensure your lower unit stays protected under all boating conditions.

Standard Gear Lube

  • Designed for everyday boating and normal operating conditions
  • Protects against corrosion and friction
  • Suitable for small to mid-size engines on outboards, sterndrives, and inboards

Heavy-Duty / High-Performance Gear Lube

  • Formulated for high-output or larger engines
  • Provides enhanced protection under heavy loads, high speeds, or frequent saltwater use
  • Offers stronger film strength, superior water resistance, and extended lower unit life

Gear Lube Maintenance Schedule

  • Break-in Service: Change gear lube after the first 20 hours of operation on a new engine
  • Every 100 Hours / Annually: Replace gear lube for boats used regularly
  • End of Season Service: Always change gear lube before storing the boat for an extended period
  • Additional Checks: Inspect the lube when draining for signs of water intrusion (the lube will be a milky color) or metal flakes (internal wear)

Learn More About Specific Brands

While this post covers general gear lube maintenance, each manufacutrer has unique recommendations, formulations, and capacity charts. For brand specific guidance, check our detailed posts for 

Questions about Crankcase Oil Capacity?

Check out our Complete Marine Engine Oil Guide for more info and capacity charts!

Still have questions or need extra help? Reach out and let our experts provide the advice you need. For quick assistance give us a call at 877-388-2628 or email sales@wholesalemarine.com and we'll be sure to get back to you promptly!