How to Winterize Your Mercury Boat Motor

Mercury outboards should be stored upright in the winter.

Winterizing your Mercury engine is absolutely critical for anyone who lives in a climate that even remotely comes close to freezing. It is not an activity that should be left until the last second, and it is always better to sacrifice a few weeks of fall boating for the peace of mind that it will run well when brought out of storage in the spring. If your outboard is small enough to carry, it should be stored indoors on a sawhorse for the winter.

Things You'll Need

• Socket set
• Screwdriver set
• Flushing device
• Bucket
• Lower unit oil
• Fogging oil
• Fuel stabilizer
• Sawhorse

Instructions

1. Park your boat on a flat surface and tilt the motor so that it is vertical.

2. Add fuel stabilizer to the gas tank. The ratio of fuel to stabilizer is 50-to-1, so it helps to have a full tank of gas so that you know exactly how much stabilizer to add.

3. Connect a hose to the water intake flushing device and connect the device to the water intake. The flushing device looks like a pair of earmuffs that fits around the lower unit. Turn the hose on and start the engine, allowing it to run for 10 minutes.

4. Disconnect the fuel line and allow the engine to burn off any remaining gas. Remove the flushing device and allow the water to drain out.

5. Remove the spark plugs and spray fogging oil into the plug holes. Crank the engine once or twice to run the fogging oil through the pistons and then replace the spark plugs.

6. Place a bucket under the lower unit and remove the gear case vent screw and the oil drain screw. This oil is very thick and will take time to completely drain. Wipe off any excess oil from the skeg once the oil has finished draining.

7. Insert the nozzle of the gear oil tube into the lower unit drain plug and start squeezing the tube until you see oil coming out from the top vent. Replace the top vent screw, and quickly replace the lower screw. Wipe up any excess oil that may have spilled.

8. Loosen the transom mounts and remove the motor if it is small enough to be carried, and store it vertically on a sawhorse, making sure to keep the skeg off the ground.

Tips & Warnings

• Touch up any nicks in the paint to prevent rust using Mercury touch-up paint.

References

• Mercury Marine: Storage Preparation
• Nitro Owners: Changing Lower Unit Oil