Lower Unit Gear Lube

Lower Unit Gear Oil - Resources & Information

When it comes to maintaining your lower unit for optimal performance and longevity of your outboard motor, replacing your Lower Unit Gear Lubricant is a must. 

PartsVu offers a complete selection of Lower Unit Gear Lube from OEM manufacturers and trusted aftermarket suppliers. Whether you need a lower unit oil change kit, gear lube extractor pumps, and bulk gear lube oil (available in 55 gallon drums), PartsVu has what you need to get the job done. 

Need help servicing your outboard engine? PartsVu regularly publishes helpful how-to guides and other valuable maintenance information to help boaters service their outboard engines. Browse PartsVu Xchange, our outboard maintenance blog, for a wide range of relevant topics, and see the FAQ section below, covering everything you need to know about maintaining your boat in confidence.

Lower Unit Gear Lube FAQ

What oil goes in an outboard lower unit?

The oil that goes in the lower unit of an outboard motor is typically a special type of oil specifically formulated for use in marine engines. This type of oil is designed to withstand the harsh conditions found in a marine environment, including saltwater, high temperatures, and high levels of moisture.

There are several different types of oil that can be used in the lower unit of an outboard motor, including:

1. Mineral oil: This is a traditional type of boat gear oil made from petroleum and is generally less expensive than other types of oil. It is suitable for use in most outboard motors, but may not offer as much protection as synthetic oils.
2. Synthetic oil: This type of oil is made from synthetic base stocks and is designed to provide better protection and performance than mineral oils. It is more expensive than mineral oil, but may be worth the extra cost for its improved performance.
3. Blended oil: This type of oil is made from a combination of mineral and synthetic oils, and is designed to offer some of the benefits of both types of oil at a lower cost.

It is important to use the correct type of outboard lower unit oil, as using the wrong type of oil can cause problems with the engine performance and even lead to damage. Always refer to your owner's manual or consult with a qualified mechanic to determine the best type of oil for your particular outboard motor.

What should I know about the color of lower unit gear oil in outboards?

The marine gear oil color in the lower unit of an outboard motor can provide some information about the condition of the oil and the health of the engine. Here are a few things to consider:

1. Fresh oil is typically a golden or amber color. If the oil in the lower unit of your outboard motor is this color, it is likely that the oil is in good condition and the engine is functioning properly.
2. Dark-colored oil may indicate that the oil is old or has been contaminated. If the oil in your lower unit is dark brown or black, it may be time to change the oil.
3. Oil that is excessively dirty or contaminated may have a grey or cloudy appearance. If the oil in your lower unit looks like this, it may be a sign that there is a problem with the engine or that the oil has been contaminated by water or other contaminants.

It is important to regularly check the lower unit oil color of your outboard motor and to change the oil as needed to ensure that the engine is running smoothly and efficiently. If you notice any unusual colors or contamination, it is a good idea to consult with a qualified mechanic to diagnose the problem and take appropriate action.

Is winterizing my outboard important?

While it’s always a bit more fun to pull out your boat than to put it away, properly winterizing your outboard engine should be mandatory for all experienced boaters. Winterizing helps avoid engine damage and will facilitate a smoother start to the beginning of next season - after all, no one wants to wait to get back on the water!

There are several important steps you should take when storing your MerCruiser outboard lower unit to ensure that it’s properly winterized.

1. Flush Your Engine - Thoroughly flush your MerCruiser engine to remove any salt buildup if you are a saltwater boater, or accumulated mud and grime if you are a freshwater boater. Failure to remove this debris from your MerCruiser lower unit leads to corrosion in the engine. And if you’re a saltwater boater, leftover salt crystals in the lower unit can act like sandpaper to your internal engine components.
2. Stabilize Your Fuel System - Fuel starts to go bad within 30 days of sitting in your fuel system. It is vital to use a fuel stabilizer when your boat will be sitting unused for more than two or three months. Adding the amount of fuel stabilizer directed on the product’s packaging to your fuel—for instance, 1 ounce of Mercury Quickstor Fuel Stabilizer for every 5 gallons of marine fuel ensures proper winterization for more than 3 months. 
3. Fog Your Engine - Fogging oil is a wax-based oil that coats the engine to prevent corrosion.
4. Change Out the Lower Unit Oil - It’s recommended by marine mechanics to change your gear lube before storage to make sure that there is no water in the lower unit’s oil. Any water in the oil could freeze, expand, and crack your lower unit. Additionally, old oil is more likely to gum up oil passages and corrode components due to changes in its chemical composition through regular use. Last, consult your owners manual for which oil is appropriate for your engine.
5. Disconnect Your Battery - Disconnect your battery and spray CRC Marine Battery Terminal Cleaner on your battery terminals.

What's the difference between gear lube vs gear oil?

Gear lube and gear oil are both types of lubricants that are used to reduce friction and wear in gears. However, there are some key differences between the two:

1. Composition: Gear oil is typically made from a base oil that is refined from petroleum, while gear lube is made from a combination of base oils and additives. Gear lube may also contain detergents, dispersants, and other additives to improve its performance and protect against wear and corrosion.
2. Viscosity: Gear oil is typically thicker and more viscous than gear lube, which means it is more resistant to thinning out under high temperatures. This makes it better suited for use in high-stress applications where the gears are subjected to heavy loads or high speeds.
3. Applications: Gear oil is typically used in applications where a high level of protection and performance is required, such as in gears that are subjected to heavy loads or high speeds. Gear lube is more suitable for use in applications where a lower level of protection is sufficient, such as in low-speed gears or bearings.
4. Compatibility: Gear oil is generally not compatible with certain materials, such as rubber or plastic, and may cause these materials to break down over time. Gear lube, on the other hand, is more compatible with a wider range of materials and is less likely to cause breakdown or degradation.

How do I perform a 100-hour service on my outboard engine?

To ensure proper engine function, it’s always best to service your outboard engine every 100 hours after the initial break-in period (first 10 hours) and after the first maintenance interval (at 20 hours). 

As an example, the following is a Suzuki outboard 100-hour service checklist to help you service your engine properly. Refer to your owner’s manual for your particular engine make and model for an exact list of 100-hour maintenance tasks:

How to find the best lower unit oil for my outboard?

To find the best lower unit oil for your outboard motor, you should consider the following factors:

1. Compatibility: Make sure that the oil you choose is compatible with your outboard motor. Some oils are formulated specifically for use in certain types of outboard motors, while others may be suitable for use in any type of outboard. Check the manufacturer's recommendations or consult with a qualified mechanic to determine the best type of oil for your specific outboard.
2. Performance: Look for an oil that is specifically formulated for use in marine engines and is designed to withstand the harsh conditions found in a marine environment, such as saltwater, high temperatures, and high levels of moisture.
3. Quality: Choose an oil that is made by a reputable manufacturer and has a proven track record of performance and reliability.
4. Price: Consider the cost of the oil when making your decision. Synthetic oils tend to be more expensive than mineral oils, but may offer better performance and protection for your outboard.
5. Availability: Make sure that the oil you choose is readily available and can be easily purchased from a local retailer or online.

Ultimately, the best lower unit oil for your outboard will depend on your specific needs and the type of outboard you have. It is always a good idea to refer to the manufacturer's recommendations or consult with a qualified mechanic to determine the best oil for your particular outboard.

Which guides should I read to learn more about marine lubes, marine oils, and marine grease?

For novice boaters, PartsVu offers a comprehensive collection of guides for marine lube, including how often you should maintain the lower unit boat oil in your particular model of outboard, best-practices, and plenty of product links to point you towards everything you need to work on your boat in confidence. Start with the following articles and use the search bar in the PartsVu Xchange for more specific topics:

Boat Gear Lubes

• Guide to Mercury Marine Precision Oils & Lubricants
• 5 Reasons To Get a Yamaha Marine Gear Lube Kit