Tips and Tricks for Winterization and Decommissioning Your Boat

Why does a boat need winter service in Wisconsin?

A boat needs winter service in Wisconsin because leftover water in engines, manifolds, heat exchangers, freshwater lines, heads, air conditioning, and bilges can freeze and crack expensive parts. Dirty oil left in an engine over a long layup also holds acids and moisture that attack internals. Fuel that sits untreated can separate or varnish. A complete fall service prevents that damage and gives you a clean look at the hull, running gear, and anodes while the boat is out of the water.

What is the difference between winterizing and decommissioning?

Winterizing is the systems work: engines, generators, drives, fuel, plumbing, heads, and climate systems. Decommissioning is the full end-of-season package—pump-out, haul, pressure wash, inspection, winterization, battery care, interior prep, covering, and storage. Most Wisconsin owners need both, not just antifreeze in the engine.

When should you schedule fall boat service?

Schedule fall boat service before the first hard freeze. Great Lakes guidance typically points to mid-October. Waiting until ice is already forming is late. Indoor heated storage still requires winterization or decommissioning of raw-water and plumbing systems unless the facility or the technician confirm otherwise. Space and haul dates fill first come first serve. CenterPointe winter storage contracts commonly run October 1 to May 1, with a deposit and signed agreement required to reserve space.

What does professional boat winterization/decommissioning include?

Professional winterization/decommissioning usually includes:

• Freshwater flush of the cooling system
• Oil and filter change so contaminated oil does not sit all winter
• Fuel stabilizer, with the tank left slightly short of full so fuel can expand 
• Antifreeze through raw-water cooling (propylene glycol / marine or RV antifreeze—not automotive ethylene glycol in potable lines)
• Fogging oil on engines that call for it
• Drain and treat freshwater tanks, heaters, faucets, showers, and ice makers
• Pump-out and treat the head and holding tank
• Bilge clean-out and a small amount of antifreeze if water cannot be fully removed
• Battery disconnection, removal or a maintenance charger
• Cover, shrink-wrap, or placement in indoor heated or outdoor storage

Manufacturer procedures vary by outboard, sterndrive, inboard gas, and diesel. Factory-certified work matters on Volvo Penta IPS, MerCruiser, Yamaha, Crusader, Kohler, Westerbeke, and similar systems.

What else should fall service cover besides winterizing?

Fall is the best time to find problems you cannot see in the slip. After haul-out and a pressure wash, inspect bottom paint, shafts, props, struts, anodes, bellows, and through-hulls. Change drive or gearcase oil and look for water in the oil. Note gelcoat, canvas, teak, and electronics issues now so they can be repaired over the winter instead of in the April rush. That is winter service in the useful sense: the boat comes out protected and goes back in better, not just parked.

How should you care for a boat in storage all winter?

Boat care in storage is simple and easy to skip. Keep snow load off outdoor covers. Check shrink-wrap vents so moisture does not sit against gelcoat and cushions. Use moisture absorbers below deck. Keep batteries charged. Do not assume “it’s inside, so nothing can freeze.” Raw-water systems and un-winterized plumbing can still fail if the building is only cool, not truly heated, or if a system was missed.

What does year-round boat maintenance look like?

Year-round boat maintenance is the work that makes winterizing cheaper and spring commissioning faster:

• Follow the engine and drive service intervals
• Keep anodes, bellows, and raw-water impellers on a replacement schedule
• Treat fuel and keep tanks reasonably full during the season
• Wash salt, silt, and scum off regularly, even on freshwater
• Service Seakeeper, HVAC, electronics, and generators before they fail on a holiday weekend
• Fix small gelcoat, canvas, and leak issues before they become structural or interior damage

CenterPointe also handles teak, paint and bottom paint, Seakeeper installs, and factory-approved repairs, so fall decommissioning can turn into planned winter work instead of a spring surprise.

Indoor heated storage vs outdoor storage

Indoor heated storage reduces freeze risk, snow load, UV, and cover damage. Outdoor storage costs less and still works if the boat is winterized correctly, washed, blocked or trailed properly, and covered with ventilation. In Door County, Milwaukee, Oconomowoc and Lake Country, CenterPointe offers both, with an on-site service department at each yard.

Frequently asked questions

Can I winterize my own boat?

You can winterize a simple outboard runabout if you follow the manual. Larger sterndrives, inboards, diesels, generators, air conditioning, and multi-fixture plumbing are easy to miss. A missed drain plug or an untreated water heater is a spring repair bill.

Do I still winterize if the boat is in heated storage?

Usually yes for raw-water circuits, unless the yard and the manufacturer process say the building stays above freezing and those systems are confirmed dry. Ask the service department; do not assume heat replaces winterization.

What antifreeze should be used in a boat?

Use non-toxic propylene glycol marine or RV antifreeze in freshwater and sanitation-adjacent systems. Do not use automotive ethylene glycol in potable water lines. Cooling systems should follow the engine manufacturer’s product and procedure.

When should I book spring commissioning?

Book it the earlier the better! Spring schedules fill up fast so don't wait until February or March to line up your winter work or spring maintenance.

Ready to schedule winterization, storage, or service? Contact CenterPointe Marine in Milwaukee, Pewaukee, Kenosha, or Door County and request service or storage at centerpointemarine.com.