Failure to winterize can cause your boat to suffer significant damage such as cracks that cause leaks, corrosion, frozen pipes, interior damage, and fuel degradation. By the time spring comes all these problems will cost you a fortune to repair, especially since most insurance policies do not cover damage done by lack of maintenance. Since no two boats are alike, the first thing to do is to check owner's manual for boat and motor manufacturer's recommendation on winterizing. To get you started here are a few simple measures you can take to assure your boating pleasure will be at peak performance come spring.
The first thing to do is to fill the gas tank to prevent unpleasant things from happening such as condensation, oxidation, and subsequent spoilage, and add enough stable to condition the fuel for storage. After the fuel is topped off, hook up your water supply hose to your "ears" and attach them to the lower unit. The "ears" are the same ones you use to flush and run your outboard with. Use these to prevent damage to your engine, while warming it up. After warming the engine, change the oil to allow impurities to drain. Your owner's manual will show the location of where to pump out your oil. Most are through the dipstick pipe, but some boats have a special pipe just for this. You need to make sure the hose runs down the pipe well into the engine sump pan.
You do not want to scrimp on the engine and oil filter. Buy the best you can, as this will protect your investment. Make sure the oil filter has a check valve in it to protect your engine from oil draining back through the filter. Most inboards require 30-weight oil; you can use an alternative multi-grade, but make sure to look in the manual for the right oil for your engine.
Oil tends to settle on the bottom of the engine block so consider fogging the carburetor while the engine is running for 20-30 seconds or until it begins to smoke. Fogging oil should be sprayed into the carburetor to reduce condensation and prevent rust from building up in internal parts of the engine. Once the engine is fogged, detach the fuel line and run the engine until all of the gas is burned. Lower the motor so all of the water drains from it, then turn it over a few times to blow out what water remains in the cooling system.
If your engine uses coolant, drain the existing fluid from the engine block and replace with non-toxic, propylene glycol base antifreeze, which is better for the environment and for your engine. You want to avoid any antifreeze that contains ethylene glycol base, which is known to release toxins into to the water.
Outboard engines require almost the same type of maintenance as inboard engines. However, experts recommend taking smaller outboards home for safekeeping because they tend to be an easy target for thieves during the winter due to the lack of people around the docks. Flush the outboard engine with fresh water using flush muffs or similar device attached to the raw water pickup. Let all water drain from the engine. Wash engine down with soap, water, and rinse thoroughly. Disconnect the fuel hose and run engine until it stops. It is important to follow a step-by-step procedure to make sure that all fuel is drained from the carburetors to prevent build-up of deposits from evaporated fuel. Use fogging oil in the cylinders to lubricate the cylinder walls and pistons right before the motor stops.
Drain the oil from the lower unit and check for any water or metallic shavings that will indicate it's time to replace seals. Make sure the lower unit is in the down position. Look in your manual for location of the drain plug and drain the oil from the unit. If your lower unit is filled incorrectly an air pocket will form inside the drive housing, and when you turn the unit over in the spring the air pocket will still be there preventing oil to the bearings, and gears resulting in expensive repairs. If you don't feel comfortable doing this, have your dealer do it for you. It is not hard to do, but you need to make sure all the air is out of the lower unit.
If you are planning on storing your boat out of the water, disconnect the battery and store it at home for easier maintenance and better protection against theft. Removing the battery is not recommended if the boat will remain in the water during the winter period. Boats left in the water should have the battery on board and functioning so the bilge pump will continue to function if needed. After taking the batteries out, clean the battery storage area in your boat.
Storing your boat ashore if you could afford it is an important process towards winterizing your boat. Storage ashore is better than storing in the water, in the long run your boat will be protected from developing blisters around the hull caused by water soaking into the laminate below the waterline. Power wash the outside of your boat and after you have cleaned all stains and sea build-up, make sure to look around the boat for places that need to be sealed, painted and varnished. This will protect your boat all winter long until the next season.
Although storing a craft ashore is beneficial towards the longevity of a boat, some people can't afford it and must keep their boat in the water through the winter. If this is the case, the first thing to do is to make sure to close seacocks and gate valves to protect thru-hulls. Failure to close thru-hulls will result in your boat sinking, costly repairs and an increase in insurance. The only thru-hull that should be open is the cockpit drains, which must be clamped with stainless steel hose. A deicing device or bubbling system should go around your boat if the boat is stationed where water tends to freeze. Don't forget to check your boat over the winter months.
Regardless if you can take your boat out of the water or not, the best thing to do is to cover it. By covering a boat, you will protect the above waterline from the wind, snow, and ice that can cause corrosion. Boat experts recommend going to your boat dealer and getting what is called mold and mildew bags, and put them in your boat. This will solve any problem of smell and extra cleaning in the spring. Make sure your cover is not torn, in good shape, and that it has a snug fit.
Following some of these suggestions will help you get your boat ready and about when spring arrives. The best way to winterize a boat is to follow an owner's manual and instructions step by step, if you plan to do-it-yourself. If you never did a winterize job on your boat it is best to seek professional help the first time. Ask questions and pay attention to the equipment they use and how the job gets done.
*Some information provided by do-it-yourself community forum members.