Oil – The Lifeblood Of Your Outboard

To keep that outboard engine running smoothly, you need to choose and use the right powerhead and lower unit oils.

The key outboard engine maintenance chores that will keep an engine running smoothly for years on end can be boiled down to a very short list: give the engine a freshwater flush after every saltwater use, use a top-notch engine and lower unit oil, and change the oils regularly according to the manufacturer’s recommendations. Take care of these simple chores, and a modern outboard will run strong for years to come – hopefully, even for decades.

outboard oil

You want your outboard to run strong for years on end? Of course, you do!

Choosing the Best Engine Oil

Choosing the best engine oil for your outboard is often as easy as tuning in to what the manufacturer recommends. Suzuki provides a good case study. They formulate oil that exceeds NMMA standards and is also formulated specifically for Suzuki outboards. ECSTAR V7000 semi-synthetic oil uses a high-viscosity, low sulfur content base oil that reduces ash buildup and maximizes efficiency. It also has additives designed to keep engine parts clean and provide thermostability whether you’re running hard in the heat of summer or turning the key while snow falls around you. While Suzuki doesn’t say using ECSTAR is a “must” for all of its outboards, it does recommend it if you want to maximize long-term reliability and optimize fuel efficiency.

ecstar oil

Using the best possible oil is a key component to treating your outboard right.

In all cases, you must – must – always make sure that the oil you put into your engine is FC-W certified. This means that the oil has been bench-tested for viscosity, corrosion protection, filter plugging, foaming, and aeration. Oils that pass these tests and then pass a 100-hour engine performance test are certified FC-W by the NMMA.

What happens if you use regular automotive oil in an outboard? Your protection level drops substantially. Most modern automotive oils are designed for running with minimal friction to peak out fuel efficiency. That’s great for an engine that turns at low rpm most of the time. But that’s not how outboards operate, so you need the oil to be resistant to sheering and thinning even as the engine is spinning at thousands of rpm for hours at a time. Automotive oils also lack the corrosion protection required by an outboard. FC-W specs include corrosion-inhibitors to protect the engine’s internals from the most humid, salt-riddled air.

Choosing the Best Lower Unit Oil

When it comes to choosing a lower unit oil, again, following the manufacturer’s recommendations is the best move by a long shot. Hypoid gears (spiral bevel gears that don’t intersect at the axis, which allow the 90-degree turn in the drive shaft), need some serious lubrication where the teeth mesh. In other words, you need the oil down there to resist massive pressure. To be considered a hypoid oil, additives which are often temperature-activated ranging from organic sulfurs to polysulfides are used. On top of these, additives designed to fight corrosion are also present.

gear oil

Lower unit hypoid oil is very different from the “regular” stuff.

Simply put, if you don’t have the correct hypoid oil in a hypoid gearbox, failure is not far away. That’s why Ecstar also has a dedicated Hypoid Gear Oil, and why outboard manufacturers, as a rule, make it quite clear that hypoid oil is a must-have, in the lower unit.

Checking and Changing Outboard Oils

Generally speaking, most manufacturers recommend you not only change your powerhead and lower unit oils at regular intervals but also check your powerhead oil before every trip. This gives you a good visual indication of the oil’s level and cleanliness on a constant basis.

outboard oil

Checking the oil prior to every trip is a smart move.

Lower unit oil is a bit more difficult to check and is virtually impossible to check if your boat lives in a slip or on a mooring. Savvy boaters do, however, make sure to watch the water’s surface as the engines are tilted down. If a sheen appears on the surface of the water, you’ll want to take the time to pull the boat and make sure the lower unit oil is full and in good shape. Remember that it’s not unusual for lower unit oil to appear dark in color after a relatively short period of use and this isn’t an indication it needs to be changed. Milky or foamy lower unit oil, however, should be taken as a serious stop-sign. It indicates that water has mixed in with the oil, and the lower unit needs to be serviced by a pro – asap.

outboard oil

Whichever part of the engine it’s going into, be sure to choose that oil carefully.

Modern outboards really are a wonder, when compared to the rattling, clanking, temperamental beasts we used to hang on our transoms.

Maintain them properly and stay on top of these oil issues, and they’ll get you out to the fish and back for years – even decades – on end.

For more tips on how to keep your outboard in tip-top shape, be sure to check out How to Make a New Outboard Engine Last Longer & Run Smoother.