How to Winterize Your Yacht: A Complete Step-by-Step Checklist

Winterization is the difference between starting your yacht up in the spring and rebuilding it. Freeze damage to a single block can cost $4,000–$15,000 to fix — far more than a professional winterization, and exponentially more than DIY. Even in mild climates, the off-season needs preparation: dampness, mold, and battery drain don't care about latitude.

This is the checklist we use, organized by system. Adapt to your boat and climate.

When to start

Begin two weeks before your first hard freeze (or the day you plan to stop using the boat in mild climates). For most of the U.S., that means starting in mid-October. Don't wait — once temps drop below freezing, anything still water-filled is at risk.

Engine

The single most expensive system to repair if winterization fails. Marine engines hold cooling water in places that crack when frozen.

For inboard / sterndrive engines:

1. Run the engine to operating temperature, then change the oil and oil filter while warm (carries away contaminants better).
2. Replace the fuel filter and fuel-water separator.
3. Drain the cooling system. For raw-water-cooled engines, drain through every petcock you can find. For freshwater-cooled, just drain the raw-water side.
4. Run propylene glycol antifreeze through the raw-water intake until it comes out the exhaust pink.
5. Fog the cylinders: spray fogging oil into each spark plug hole or the intake while running.
6. Disconnect the battery, top up to 12.7V+, store on a trickle charger or in a heated space.

For outboards:

1. Run on muffs with engine flush mixed in for 5 minutes.
2. Add fuel stabilizer to a full tank, run for 10 minutes to circulate.
3. Fog the cylinders (spray into the air intake while running until it stalls).
4. Drain the gear case, refill with fresh gear oil. Check the drained oil — milky oil means a leaking seal.
5. Lubricate the throttle/shift linkages.
6. Lower the engine fully so any trapped water drains out.

Plumbing & freshwater

Anything water-filled must either be drained or filled with non-toxic antifreeze.

1. Drain the freshwater tank completely.
2. Run all faucets (hot and cold) until empty.
3. Pour 2–3 gallons of pink antifreeze into the freshwater tank, run each faucet until it comes out pink.
4. Don't forget the hot-water heater — bypass it OR drain it, then fill with antifreeze.
5. Same for the head: pump antifreeze through both wash-down and discharge.
6. Drain the holding tank and add antifreeze.
7. Drain the bilge pumps; pour antifreeze into bilges so any pockets get protected.

Hull & deck

1. Wash the entire boat thoroughly — salt left over winter is much harder to remove in spring.
2. Wax topsides if you didn't already.
3. Inspect the hull for blisters, scratches, anything you'll want addressed at spring haul-out.
4. Open all drains and lockers; remove standing water.
5. If hauling out: support stands every 8–10 feet; one keel block under hull centerline. Inspect once monthly during winter.

Interior

1. Pull all linens, towels, food, drinks, and toiletries. Mice will find anything edible by January.
2. Open all cabinet doors, drawers, refrigerator, and head doors so air circulates and mildew doesn't grow.
3. Place moisture absorbers (DampRid or similar) throughout the cabin — one per cabin minimum.
4. Vacuum and wipe down all surfaces. Mildew loves any organic residue.
5. Tilt cushions on edge or remove them entirely.
6. Open the head's seacocks if hauled, close if in water (depending on your shrinkwrap setup).

Electrical

1. Disconnect house and starter batteries, top to full charge, store on a trickle charger if possible.
2. If batteries stay aboard: ensure all switches OFF, especially bilge pump if hauled.
3. Cover or seal electrical panels against moisture.
4. Disconnect shore power.

Cover or shrinkwrap

In freezing climates, shrinkwrap is the gold standard — it sheds snow, blocks UV, and prevents standing water. Budget $20–$30 per linear foot for a quality wrap with vents. DIY canvas covers work for milder climates but require more babysitting.

Whichever you use:

• Vents matter. Trapped moisture creates mildew faster than no cover at all. Each shrinkwrap should have 2–4 vents minimum.
• Don't cover until the boat is dry. Sealing in wetness guarantees a moldy spring.
• Remove anything that traps water on deck: fenders, dock lines, anything organic.

In-water vs. hauled

The choice depends on climate and use case:

• Hauled: safer for hull, mandatory if water freezes solid. Costs $200–$1,000 for the haul + storage. Easier inspection.
• In-water with bubbler: practical in salt water that doesn't freeze hard. Bubblers (de-icers) cost $200–$500 + electricity. Watch hull electrolysis carefully.

What it costs to skip steps

Real numbers from common spring surprises:

• Frozen engine block: $4,000–$15,000
• Cracked head/intake manifold: $1,500–$5,000
• Burst freshwater pump: $200–$400 + flooded interior cleanup
• Mildew throughout cabin upholstery: $2,000–$8,000 to clean or reupholster
• Battery replacement (drained beyond recovery): $300–$1,200 for a bank

A pro winterization is typically $300–$800. Worth it if the alternative is any of the above.

Spring de-winterization

Mark a calendar reminder for late March: when you reverse this process, you'll thank past-you for following the steps in order.

For shops in your area to handle this if you'd rather not, browse our boat repair directory and look for shops offering engine and plumbing service.