How to Change Gear Lube on a Yamaha Outboard Engine

[@WPapsky]

Hey Frank. I recently changed my lower unit gear lube. It came out someone caramel/milky. I refilled and ran for a month and checked again and same thing. Came out pretty caramel colored and milky. I did a pressure test at 8lbs over night and no drop in pressure. Any thoughts?

[@partsvu]

Hey, Thanks for watching! Finding caramel-colored or milky gear lube in your lower unit usually indicates the presence of water, which can be concerning. However, given that your pressure test didn't show any loss in pressure, there are a few potential reasons and considerations to explore: 1. Residual Water Contamination Even after changing the gear lube, some residual water could have remained in the lower unit. If not thoroughly drained or if water was still present in pockets within the unit, it could mix with the new lube, causing it to appear milky again. 2. Small Leaks While an 8-pound pressure test overnight showed no drop in pressure, it's possible that small, intermittent leaks might not have been detected. Consider running a higher pressure test, closer to 15-20 psi, for a few hours and also performing a vacuum test to check for minor leaks. 3. Condensation In some cases, condensation can build up inside the lower unit, especially if the boat is used in cold water or if it undergoes frequent temperature changes. This can cause the gear lube to become milky over time. 4. Oil Seal Issues Even if your pressure test was successful, the oil seals around the propeller shaft or driveshaft could be marginally allowing water to enter when the unit is in use. Inspect these seals for wear or damage. 5. Vent Plug and Drain Plug Seals Check the condition of the O-rings or gaskets on your vent and drain plugs. If these seals are worn out or damaged, they can allow water to seep into the lower unit. If this is causing concern consider visiting a certified tech for more help! Good luck Buddy.

[@AchikSarih]

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