Winterizing Your Mercury 4-Cylinder Inboard: Step-By-Step Guide

Winterizing your boat engine is essential, especially if you live in a cold climate. Freezing weather can cause costly damage to an engine that isn't winterized properly. Even in milder climates, the end of the boating season is a great time to take care of annual maintenance that will keep your engine running reliably. Here are some steps to winterize a Mercury 4-cylinder inboard boat engine and ensure it's ready to go next spring.

How to Winterize a Mercury 4-Cylinder Inboard Boat Engine

Treat the fuel system

Treating the fuel system is an essential step in winterizing your Mercury 4-cylinder inboard boat engine. Here are the detailed steps you should follow:

Step 1: Change the Fuel Filter

Start by changing the fuel filter. This is a crucial step to ensure the fuel system's efficiency and to prevent any contaminants from entering the engine. It is recommended to use a high-quality fuel filter suitable for your engine. Make sure to refer to your owner's manual for specific instructions on changing the fuel filter.

Step 2: Add Fuel Stabilizer

The next step is to add a fuel stabilizer to your fuel tank. Fuel stabilizers help prevent the fuel from breaking down and keep it fresh during the storage period. It is important to use a stabilizer suitable for long-term storage and compatible with the type of fuel you are using. Follow the instructions on the product's packaging for the correct amount to add.

Step 3: Run the Engine with Stabilized Fuel

After adding the fuel stabilizer, run the engine for a few minutes. This step ensures that the stabilized fuel circulates through the motor and the entire fuel system. It is recommended to run the engine for at least 10-15 minutes to ensure that the stabilizer reaches all parts of the fuel system.

Step 4: Check for Stale Fuel

If your boat has been in use and there is still some fuel left in the tank, it is important to check for stale fuel. Stale fuel can cause issues with engine performance and may contain contaminants. If the fuel in the tank is more than a month old, it is recommended to have it pumped out and replaced with fresh, stabilized fuel.

Step 5: Refill with Fresh Fuel

If you have an older boat with a vented fuel tank, it is advisable to fill the tank with fresh fuel. This helps prevent condensation from forming inside the tank during storage. Fill the tank to about 95% capacity, leaving some room for expansion as extreme temperature changes can cause the fuel to expand. If possible, use ethanol-free fuel, such as REC-90, which is specifically designed for recreational engines.

Step 6: Treat Fuel with Mercury Quickstor

Add a fuel stabilizer like Mercury Quickstor to the fresh fuel in your tank. This product is designed to optimize fuel performance, remove any leftover deposits from the engine, and protect the fuel system during the winter months. Follow the instructions on the packaging for the correct amount to add based on the volume of fuel in your tank.

Step 7: Run the Boat to Circulate Treated Fuel

Finally, run the boat for about 10 minutes, either in the water or while connected to a garden hose, to circulate the treated fuel throughout the fuel system. This step ensures that the stabilized fuel reaches all components of the fuel system, protecting them from corrosion and maintaining their performance.

By following these steps, you will effectively treat the fuel system of your Mercury 4-cylinder inboard boat engine, ensuring that it is ready for storage during the winter months and will perform reliably when you take your boat out again in the spring.

Change the oil and filter

Changing the oil and filter is an essential step in winterizing your Mercury 4-cylinder inboard boat engine. Here's a detailed guide to walk you through the process:

Warm-Up and Preparation:

Before you begin, it's important to warm up the engine by letting it run for a few minutes. This helps to warm the oil, making it easier to drain. Once warmed, turn off the engine and allow it to cool down to avoid any accidental burns during the process.

Gather Your Tools and Materials:

Ensure you have all the necessary tools and materials before starting. You'll need a socket wrench, oil-filter socket, drain pan, oil-filter funnel, clean rags, and 4-stroke engine oil. Having these items readily available will make the process smoother and more efficient.

Position the Engine:

Tilt the engine to the trailering position and orient the drain hole downward. This positioning ensures that the old oil drains out efficiently.

Drain the Old Oil:

Carefully remove the drain plug to allow the old oil to drain into a suitable container. Once the oil has drained completely, it's important to lubricate the seal on the drain plug with oil before securely reinstalling it.

Change the Oil Filter:

Place a cloth or a drip pan beneath the oil filter to catch any drips. Then, unscrew the old filter by turning it counterclockwise. Apply a thin layer of clean oil to the filter gasket, avoiding the use of grease. Now, you can attach the new filter. Screw it in until the gasket contacts the base, and then tighten it three-quarters to one full turn.

Add Fresh Oil:

With the new filter in place, it's time to add fresh oil. Remove the oil-fill cap and pour in the recommended engine oil to the appropriate operating level. Refer to your owner's manual or maintenance decal for precise information on the recommended oil type and capacity.

Engine Run and Final Checks:

With a water supply available, start the engine and let it idle for a few minutes while checking for any leaks. Turn off the engine and use the dipstick to verify the oil level. If necessary, add more oil until you reach the correct level.

It is important to note that while the principles of changing oil are similar across different marine engines, it is crucial to adhere to manufacturer-specific instructions. Always consult your Mercury 4-cylinder inboard boat engine manual for precise directions relevant to your particular model.

Protect the engine internals

To protect the engine internals of your Mercury 4-cylinder inboard boat engine during winterization, you should treat the engine with engine oil or fogging oil to prevent corrosion.

First, remove the spark plugs and inject approximately one ounce of engine oil or spray fogging oil directly into each cylinder, following the directions on the can. Use a fogging oil product that is specially designed for use during winterization, such as Quicksilver Storage Seal.

Next, rotate the engine flywheel manually a few revolutions to distribute the oil or spray evenly and replace the spark plugs.

Fogging oil is a wax-based oil that coats the engine and prevents corrosion. It is important to note that this process is called "fogging" the engine as it will produce plenty of white smoke.

Additionally, it is recommended to change the engine oil and oil filter regularly. Old oil can expose internal engine components to moisture and acidic combustion byproducts, which can lead to corrosion.

Grease the prop shaft

Greasing the propeller shaft is an important part of routine boat maintenance. It helps to reduce wear and tear on the drive system and increases the life of the shaft, ensuring that your boat runs smoothly.

Step 1: Removing the Propeller

Use a spanner wrench or large adjustable wrenches to loosen and remove the bolts, depending on the type of prop hub you have.

Step 2: Cleaning the Propeller Shaft

Rinse off the propeller shaft with fresh water to remove any dirt or debris. Then, use a brush to scrub away any rust spots or corrosion on the surface. Finally, rinse off all residue with a rag soaked in solvent.

Step 3: Grease Application

Before applying grease, check for any damage or rust. If there is any wear and tear, address it before continuing. Identify the areas on the shaft that need to be greased and apply a small amount of grease, slowly rotating the shaft to ensure an even layer. Use a clean cloth to wipe away any excess grease.

Step 4: Reinstall the Propeller

Before reinstalling, ensure that all components are properly aligned and secured with nuts and bolts. Check that no debris has been left behind, and if there is, use a stiff brush to remove it.

Some additional tools you may need for this process include a ratchet wrench with a deep-well socket or a Quicksilver Floating Prop Wrench, and either a Quicksilver Floating Prop Block or a block of wood to keep the propeller from spinning while you work.

It is important to use a marine-grade grease or lubricant that is designed for saltwater environments. This will help to protect against corrosion and ensure optimal performance.

Store the engine upright

When storing your Mercury 4-cylinder inboard boat engine for the winter, it is important to store the engine upright. This is because water left inside the engine can freeze and cause damage to the engine block, lower unit, and other components. By storing the engine upright, you allow any remaining water to drain out of the engine and prevent it from freezing inside. This can be done by tilting the motor up until it is vertical and securing it in place using a motor support bracket or transom saver.

Additionally, storing the engine upright can help prevent any debris or critters from getting inside. It is also important to cover the engine with a protective cover to prevent any dust or debris from getting inside. This will ensure that your engine stays in good condition during the winter and will be ready to use again in the spring.

It is also recommended to check the engine periodically throughout the winter to ensure that it is still in good condition. This includes checking the fuel tank and lines for any leaks, as well as inspecting the engine for any signs of damage or corrosion. By doing this, you can catch any potential issues early on and prevent them from becoming more serious.

Frequently asked questions