Winterizing Tips For I/O and Sterndrive Boats: Part 3

In the first and second posts we discussed flushing the engine, winterizing the engine with antifreeze, treating the fuel for winter storage and fogging the engine. This post will talk about servicing the outdrive, checking and changing the outdrive oil in a mercruiser alpha 1 outdrive.

For this part you will need: outdrive oil, a pump to fill the outdrive, new gaskets for the vent and drain screws and tools to remove the screws and prop. You will also need shop towels and an oil pan.

Remove the prop and inspect the prop shaft for any damage and for things like fishing line wrapped around the shaft. If line is wrapped around the shaft inspect the shaft seal after removing the line for damage or leaks. If a leak is found have the seal replaced and pressure check the outdrive. Grease the shaft and replace the prop.

Locate the vent and drain screws on the outdrive. The vent screw will be on the upper part of the drive leg and the drain will be near the bottom close to the water intake holes. Place a catch pan under the drive and place the drive in the full down position. Remove the bottom screw then remove the top screw. Inspect the oil! If it has white streaks or is the color of coffee with milk remove the drive and have it pressure tested by a mechanic. If it is dark black you waited to long between oil changes. The drain plugs are magnetic inspect them for metal shavings an inspect the oil for metal shavings. If metal is found have the drive inspected by a professional. If the old oil has a foul smell or is dark grey this indicates overheating or an internal failure of the drive and will require professional help.

Once the oil has drained from the drive attach your oil pump to the bottom drain hole. The pump has a threaded connector that screws into the drain hole. I find it easier to attach the connector to the outdrive before you put the pump into the bottle of gear oil.  Attach the pump to the oil bottle and pump oil into the drive until it flows out of the top hole. Replace the gasket on the top hole screw and screw the plug back into the drive. This will create a partial vacuum and let you quickly remove the oil pump from the bottom hole and place the bottom screw with a new gasket back into the drive. A small amount of oil may leak out before you can fully tighten the screw and this is ok. Using your shop towels clean up any oil that spilled on or down the drive leg.

Inspect the bellows and shift cable along with the water intake hose. If it’s been a few years since they have been replaced or if there is any dry rot or damage to the bellows have them replaced. A leaky bellows will sink a boat in record time! Here is a link to a decent alpha 1 bellows kit.

Check and replace the sacrificial anodes if they show less than 70 percent.

  • Zinc Alloy Anodes = Salt water only
    • Not recommended for use in fresh water
  • Aluminum Alloy Anodes = Salt, Fresh or Brackish water
    • Not recommended, but can be used in fresh water
    • Proven to last longer than zinc due to increased capacity
  • Magnesium Alloy Anodes = Fresh water only
    • The only alloy proven to protect your boat in fresh water

There are many types and models of outdrives. Some have a remote oil reservoir and will require addition steps to change the oil. This is a basic guide for mercruiser alpha 1 drives though the steps are generally the same for other brands such as OMC and Volvo.

Store the outdrive in the down position. This keeps water from collecting in the prop hub and possibly freezing and damaging the hub. It also reduces stress on the bellows and shift cable.