Winterizing

Belowdecks

Pump out holding tank and add antifreeze to head
Drain water heater
Drain freshwater system and run antifreeze through it
Run antifreeze through refrigeration, deck washdown pump, etc., per owner’s manual
Drain shower sump and other places where water pools
Remove food
Open lockers to air
Take home cushions or store on their sides
Take home portable electronics
Verify bilge pump and switch operate properly
Clean and dry bilges
Secure all ports and hatches
Turn off all circuit breakers

In the water

Close all seacocks 
Plug exhaust ports
Check docklines and chafe guards – center boat in slip Add or adjust fenders for proper placement

Before you go

Cover/shrinkwrap boat
Lock cabin and leave spare key with marina manager

Installed generator

Change oil and filter
Change fuel filters/separators
Check coolant level in freshwater-cooling system and add coolant if necessary
Run antifreeze through raw-water-cooling system
Make sure water strainers are filled with antifreeze

Other systems

Flush and fill air conditioning system with antifreeze

Outboards

Fill installed fuel tanks and add stabilizer
Turn off fuel supply and fog while running
Drain gear case and add fresh lubricant
Flush engine with fresh water
Store unit in lowest position Inspect/replace anodes