Preparing a powerboat for off-season or long-term storage is an important process that will both protect the boat and its engine from damage and make it ready to use when it’s time to get back on the water. Some of the steps are intended specifically to prevent damage that can occur when off-season temperatures are likely to fall below freezing, which is why in those climates it’s common to say a boat has been “winterized.” Even if the boat is kept in a warm climate or heated storage, following the off-season or long-term storage guidance outlined in your engine and boat owner’s manuals is important for maintaining boat performance and reliability. These storage steps usually include annual maintenance that should be completed even if the boat is not going to be put away for the off-season. In the long run, this maintenance can save you money and aggravation down the road.

By the Book

The separate owner’s manuals for your engine and boat are your best basic guides for long-term storage procedures. Both will have a maintenance schedule and instructions on how to complete essential maintenance tasks that most owners can accomplish. A copy of the service manual for your engine will have more detailed step-by-step maintenance instructions than the owner’s manual and can be a great guide for a dedicated do-it-yourself owner. Some storage tasks, such as flushing an inboard engine cooling system with antifreeze, are probably better left to a marine service center. Of course, you can choose to have a service center handle the entire off-season storage process. Owner and service manuals are often available for order or free download from the manufacturer’s website, or a copy can be ordered from a dealer.

Engine Basics

These are the basic maintenance points for long-term engine storage. Follow your owner’s manual for instructions specific to your engine.

• Oil Change: Most four-stroke outboards and sterndrive engines require an oil change either annually or every 100 hours of operation. Change engine oil before long-term or off-season storage, even if your seasonal use is not near 100 hours. During operation engine oil accumulates acidic combustion byproducts that can be harmful to internal engine components if left in the engine during storage. Always change the oil filter when you change the oil. Quicksilver® 4-Stroke Marine Engine Oils feature a blend of high-quality base stocks and additives formulated specifically for use in most four-stroke outboard, sterndrive and inboard, and PWC marine engines. Quicksilver oil filters for outboard, sterndrive and inboard engines are designed to maintain maximum oil flow rate and feature high pleat counts for superior filtration levels. Canisters are heavy-duty steel with a durable, corrosion-resistant powdercoat finish. Always dispose of waste oil properly at an oil recycling facility.
• Gearcase Lubricant: The gear lube in outboard and sterndrive lower units should be changed annually or every 100 hours. Replacing the lubricant removes diminished additives and contaminants and provides an opportunity to inspect the lubricant for water – any water present could freeze and damage the gearcase casting. If water drains from the gearcase, or the lubricant appears cloudy or milky, have the gearcase inspected by a professional technician. Water may be entering the gearcase through a failed propeller shaft seal, which can cause serious and expensive damage to internal components. Quicksilver Gear Lubricant products have a specialized marine additive package that outperforms automotive gear oil in marine gearcase applications. See your owner’s manual for specific recommendations.
• Fuel Filter: Change the low-pressure fuel filter on the engine and install a new element on a remote fuel filter if your boat has one. Quicksilver offers fuel filters for many marine engine applications.
• Stabilize Fuel: At the end of the season try to run your boat fuel tank almost empty and then add fresh fuel (ethanol-free if available) treated with a marine stabilizer product such as Quicksilver Quickstor® Fuel Stabilizer. Add the appropriate amount of stabilizer based on the instructions on the bottle. To get that treated fuel into the entire fuel system, run the engine for about 10 minutes, either in the water or while connected to a garden hose (follow owner’s manual instructions if using a hose).
  
  If you have an older boat with a vented fuel tank, it’s a good idea to fill the tank with fresh fuel to keep condensation from forming in the tank during the off season. Stop when the tank is about 95 percent full because extreme temperature changes over the winter can cause the fuel to expand, potentially forcing gas out of the vent. The fuel tanks on most newer boats can’t freely vent to the atmosphere and won’t collect moisture from the air. Non-vented tanks don’t need to be filled, but the fuel in them should still be treated with fuel stabilizer.
• Protect Internal Components: After you are done running the engine, remove each spark plug and spray an ounce of Quicksilver Storage Seal into each cylinder, which forms a protective barrier to prevent rust on internal metal surfaces. Crank the engine through one revolution to distribute lubricant throughout the cylinders. Replace the spark plugs. Quicksilver Storage Seal can also be used to fog two-stroke engines, following owner’s manual instructions.
• Power Trim and Steering Fluid: Check power trim fluid and top off if necessary with a marine-specific product such as Quicksilver Power Trim and Steering Fluid, following the instructions in your owner’s manual. Also check the power steering fluid level.
• Propeller Shaft Inspection: Remove the propeller and inspect the propeller shaft and propeller shaft seal area for fishing line. Lubricate the propeller shaft with Quicksilver 2-4-C Marine Grease. If the boat will be stored in a public area, consider storing the propeller in a secure place to prevent theft.
• Anodes: Inspect sacrificial anodes and replace when about half the anode has been lost to corrosion.
• Touch Up: To prevent corrosion, touch up the paint on external surfaces, especially if the paint on the gearcase or skeg has been worn to bare aluminum. Quicksilver paint products are a perfect color match for the original paint on Mercury® or MerCruiser® engines and are formulated for the marine environment with UV blockers that are not usually found in standard hardware store spray paint.
• Corrosion Guard: For maximum corrosion protection spray Quicksilver Corrosion Guard Heavy Duty rust inhibitor on the outdrive, gearcase, tilt and trim motor, exposed electrical connections and other surfaces that live under the water. Do not cover anodes. Apply Quicksilver Corrosion Guard Engine Protect to the engine block and to under-cowl areas of an outboard motor.
• Upright for Storage: Always store an outboard in a vertical (upright) position to allow water to drain from the motor. Trim a sterndrive outdrive down for long-term storage. Water trapped in cooling passages or rainwater collected in the propeller exhaust outlet can freeze and cause damage. Do not cover an outboard with water-tight plastic.
• Purge Water: Unlike outboard motors, inboard and sterndrive engines are not self-draining. Any water left in the engine cooling system could freeze and damage the engine block or other components. See your owner’s manual for the recommended method of purging water from the system. Some late-model engines are equipped with an air pump that is used to purge the system. Other engines require that an antifreeze solution is circulated through the engine while it is running to displace water from the system.

Boat Basics

Many boats have some systems that need to be prepared for long-term storage, especially if below-freezing temperatures are likely. The off-season is also a great time to tend to any maintenance issues, such as restoring bottom paint, or to make upgrades to your boat, such as installing new electronics.

• Battery Storage: Off-season maintenance is critical for maximum battery life. Allowing a battery to remain in a fully discharged state during the off-season causes it to become sulfated, in which case it will need to be replaced. Before off-season storage, completely charge the batteries and then disconnect the terminals so nothing can draw the batteries down. If there’s power available at your storage site, connect the batteries to a “smart” battery maintainer/charger through the off-season. If your boat has an onboard charger it will maintain the batteries. Leave the charger connected to the batteries. If there is no power at your storage site, remove the batteries from the boat and store them where they can be connected to a maintenance charger.
• Store It Dry: Go through the entire boat and remove any gear from storage compartments and cabinets. Choose a warm dry day and park the boat in the sun with all hatches open to allow storage compartments and the engine bay to dry completely, especially those lined with carpet. Life jackets and other gear that is left in the boat can become mildewed over the off-season. Remove tubes of sunscreen, old fishing bait and any trash that could attract rodents over the winter.
• Purge Water: To prevent freeze damage, water should be purged from all raw water accessories that have pumps, including livewells and bait wells, washdowns, and water ballast systems. Follow the instructions in your owner’s manual. In some cases, these systems can be cleared with compressed air. Others may need to be purged using environmentally safe RV antifreeze.
• Purge the Plumbing: To protect freshwater plumbing from freeze damage, open all the faucets or outlets with the pump running and wait until they go dry. Then close them back up, shut the pump off and add environmentally safe RV antifreeze to the water tank. Next, open the faucet farthest from the tank, turn the pump back on and let it run until antifreeze comes out of the faucet. Close it, go to the next-farthest outlet and do the same. Repeat the process until antifreeze is running through all the pipes and faucets and your boat’s plumbing systems are fully protected. Consult your owner’s manual for instructions specific to your boat.
• Secure Soft Parts: If you have a dry place like a garage or basement where you can stow the boat cushions, canvas and curtains, pull them off and bring them indoors. Keeping them in a humidity-controlled environment will help prevent mold and mildew, extend their useable life and keep them from developing musty odors. If your boat has clear canvas curtains, remember to roll them up rather than folding them so creases don’t develop over the winter. If the boat will be stored in an area where rodents could be a problem, consider adding mothballs or scented dryer sheets to a few of the compartments. The smells they give off will help deter critters from setting up house inside of your boat.
• Keep It Dry: It’s important to keep water, which can cause the formation of mildew and corrosion, from entering the boat during the off-season. The best option is storing the boat in a garage or indoor facility. If that’s not possible and the boat will be stored outdoors, consider having the boat professionally shrink wrapped. Shrink wrap will completely seal out snow and rain and will keep dirt and leaves from collecting in the boat. The installer may construct a temporary structure under the shrink wrap to support the load of snow. For long-term storage shrink wrap is usually more weatherproof than your boat’s canvas cover, and you’ll get more years of use out of the canvas cover if it’s not exposed to the elements all winter. The shrink wrap installer should add vents to prevent condensation from building up inside the boat. If the boat is stored outdoors, remove the drain plug. When possible, position the boat with its bow elevated – by raising the trailer tongue jack, for example – so that any water that may enter the boat will run aft and out the drain. Leave the drain plug in an obvious place, such as hanging from the steering wheel, so you don’t forget to install it before launching the boat next season.

A properly stored boat will be safe from damage over the off-season, and ready to launch come spring. You’ll be back on the water and having fun in no time.