Winterizing Your Suzuki Outboard: A Step-by-Step Guide

Taking a few hours to winterize your Suzuki outboard can save you from expensive repairs and frustrating startup issues next spring. Cold temperatures, stale fuel, and moisture are your engine’s biggest enemies during storage. The good news? Most boaters can handle winterization themselves with basic tools and the right supplies.

This guide covers the full winterization process for Suzuki 4-stroke outboards, including EFI models. We’ll walk through each step in order so you can protect your investment and hit the water confidently when warmer weather returns.

What You’ll Need

Before you start, gather these supplies:

Fresh engine oil (check your owner’s manual for the correct weight and capacity)
New oil filter (model-specific)
Lower unit gear lube
Fuel stabilizer
Fogging oil
Flush muffs (“ear muffs”) or access to a flush port
Garden hose
Basic hand tools (socket set, crescent wrench, drain pan)
Marine grease and grease gun
Corrosion inhibitor spray
Replacement spark plugs (optional but recommended)

Step 1 – Flush the Cooling System

Flushing removes salt, sand, and mineral deposits that corrode internal passages during storage. This step is critical for saltwater boaters and recommended for freshwater use.

To flush your Suzuki outboard:

Attach flush muffs to the lower unit water intakes or connect a garden hose directly to the flush port (if equipped).
Turn on the water supply and ensure steady flow.
Start the engine and let it idle in neutral.
Run for 5 to 10 minutes, allowing water to circulate through the entire cooling system.
While the engine runs, check that water is flowing from the tell-tale (indicator stream).

If using flush muffs on a Suzuki, the small, round soft-style muffs tend to seal better than rectangular designs due to the shape of the lower unit. Make sure you have a good seal before starting the engine.

Step 2 – Stabilize the Fuel System

Ethanol-blended fuel degrades in as little as 30 days, leaving varnish and deposits that clog injectors and carburetors. Fuel stabilizer prevents this breakdown and keeps your fuel system clean through the winter months.

To stabilize your fuel:

Add the recommended amount of fuel stabilizer to your tank (follow the product label for the correct ratio).
If possible, fill the tank to reduce the air space where condensation can form.
With the flush muffs still attached and water running, restart the engine.
Run the engine at approximately 1,500 RPM in neutral for 10 to 15 minutes. This circulates the stabilized fuel through the entire system, including the vapor separator tank (VST) and injectors on EFI models.

Choose non-ethanol fuel if available. It stores longer and causes fewer issues. Either way, don't skip the stabilizer.

Step 3 – Change the Engine Oil and Filter

Old engine oil contains acids and contaminants that corrode internal components during storage. Fresh oil provides a protective film, so your engine is ready to run cleanly in the spring.

To change your engine oil:

Run the engine briefly to warm the oil (this helps it drain completely).
Locate the oil drain plug and place a drain pan beneath it.
Remove the drain plug and allow the oil to drain fully.
Remove and replace the oil filter.
Reinstall the drain plug with a new washer if needed.
Refill with the correct weight and quantity of oil (refer to your owner’s manual).
Check the oil level with the dipstick and top off as necessary.

If the old oil looks milky or has a burnt smell, investigate further. Milky oil could mean water contamination, while a burnt smell suggests overheating. Both conditions require attention before storage.

Step 4 – Fog the Engine (Cylinder Protection)

Fogging oil coats the cylinder walls, pistons, and valves with a protective film that prevents corrosion during extended storage. This step is especially important if your boat’s going to be stored for more than 60 days.

Important note for EFI 4-stroke owners: don't spray fogging oil into the air intake on electronic-fuel-injection engines. This can damage sensors and gum up injectors. Instead, fog directly through the spark plug holes.

To fog your Suzuki 4-stroke:

Remove all spark plugs using the appropriate socket.
Spray a 2- to 3-second burst of fogging oil into each cylinder through the spark plug hole.
With the spark plugs removed and the safety lanyard disconnected, crank the engine briefly (1 to 2 seconds) using the starter. This distributes the fogging oil across the cylinder walls.
Reinstall the spark plugs. Consider replacing them with fresh plugs, as fogging oil can foul electrodes. This gives you a cleaner start in the spring.

Some boaters skip fogging on modern 4-strokes, relying on fresh engine oil and fuel stabilizer. If you store your outboard in a cold or humid environment, the extra protection is worthwhile.

Step 5 – Service the Lower Unit

Water can enter the lower unit through worn seals during the boating season. If that water freezes, it can expand and crack the gearcase housing. Changing the gear lube removes any trapped water and provides fresh lubrication for the gears.

To change the lower unit oil:

Position a drain pan beneath the lower unit.
Remove the lower (drain) screw first, then the upper (vent) screw. The oil will begin draining once both are removed.
Allow the oil to drain completely and inspect its condition.
If the oil appears milky or contains metal shavings, your lower unit may have a seal leak or internal damage. Have it inspected by a qualified technician before storage.
Refill the lower unit from the bottom drain hole using a gear lube pump. Pump slowly until oil begins flowing from the upper vent hole.
Replace the upper screw first, then the lower screw. Use new gaskets or washers on the drain plugs.

Step 6 – Lubricate Moving Parts

Grease fittings and pivot points can seize or corrode if left dry during storage. A few minutes with a grease gun prevents problems and ensures smooth operation in the spring.

Grease the following points:

Swivel bracket
Steering tube
Tilt mechanism
Trim rams (wipe with a light coat of marine grease)
Cowling latches
Propeller shaft (remove the prop, clean any fishing line from the shaft, apply grease, and reinstall)

Don't forget to spray the powerhead and exposed wiring with a silicone lubricant or corrosion inhibitor. This protects electrical connections and metal surfaces from moisture.

Step 7 – Protect and Store

Proper storage conditions extend the life of your winterization efforts.

Final steps:

Inspect and replace zinc anodes if they're more than 50% eroded. Sacrificial anodes protect other metal components from galvanic corrosion.
Touch up any chipped or missing paint to prevent rust.
Apply a coat of marine wax to the exterior finish.
Cover the propeller exhaust outlets with plastic bags or tape to keep pests and moisture out.
Store the engine in the vertical (down) position. This lets any residual water to drain from the cooling system and prevents water from pooling in the exhaust.
Choose a dry, well-ventilated storage area with consistent temperatures. Avoid storing near heaters or furnaces, which can cause condensation.

Taking the time to properly winterize your Suzuki 4-stroke outboard protects your engine from corrosion, fuel degradation, and freeze damage. It also ensures a hassle-free startup when spring arrives. Most boaters can complete the entire process in an afternoon with basic tools and the right supplies.

Need parts for your winterization project? Browse our selection of Suzuki maintenance kits, oils, and filters at Suzuki Outboard Team. We stock what you need and ship fast so you can get your outboard buttoned up before the cold sets in.

Questions about winterizing your specific Suzuki model? Reach out to our team. We’re here to help.