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Why You Should Change Your Lower Unit Oil Every Year Changing your engine oil is a maintenance item most boat owners remember. Lower unit oil, however, is often overlooked. The lower unit, also called the gearcase, contains a set of precision gears and bearings that transfer power from the engine to the propeller. Unlike the powerhead, these components are completely dependent on clean gear lube for lubrication and protection. Replacing lower unit oil every year is one of the easiest and most af …

Draining your lower unit oil is one of the simplest ways to check the health of your gearcase. If the gear lube comes out looking creamy, gray, or milky instead of its normal color, it's a sign that water has entered the lower unit. While finding milky oil isn't something to ignore, it also doesn't automatically mean you need a new lower unit. The important thing is understanding why it happened and addressing the problem before more serious damage occurs. Why Does Lower Unit Oil Turn Milky? Ge …

SAE 90 vs 80W 90 Marine Gear Lube SAE 90 and 80W 90 marine gear lubes can have similar viscosity at operating temperature, but they are not always interchangeable. The correct choice depends on the lower unit design, manufacturer guidance, and whether the oil is specifically formulated for marine use. Lower units operate in harsh conditions. They are submerged, exposed to water intrusion risk, and experience high load at low speeds. Using the wrong gear lube can lead to accelerated wear, corrosi …