Working through a thorough decommissioning process when you leave your boat will reap its rewards when you return a few months later.  Here are some suggestions:-

Systems

• Air conditioning units – fresh water flush
• Batteries – top off water if appropriate and organise battery maintenance requirements
• Bilge pump float switches – clean and check
• Engine – fresh water flush, change oil and filter. Remove exhaust from elbow as appropriate.
• Fuel tanks – top off and add bio-cide additive if appropriate
• Generator – fresh water flush, change oil and filter.  Remove exhaust from elbow as appropriate.
• Holding tanks – empty
• Outboard – fresh water flush & run carburetor dry, clean, store.  Remove unused fuel.
• Propane – turn off
• Syphon breaks – service
• Watermaker – pickle

Deck, Sails, Rigging, Canvas

• Anchor Locker & chain – clean and check chain markers
• Canvas – wash dry and stow if appropriate
• Cockpit cushions – wash dry and stow
• Cockpit Instruments – cover
• Dinghy – wash dry cover stow
• Fenders, MOB equipment, barbeque/grill – wash dry and stow
• Running rigging (and dock lines if appropriate) – remove, wash dry and stow
• Sails – wash dry and stow

Housekeeping

• Bilges – clean
• Bug & ant poison – set traps
• Bunk cushions – clean if required and leave propped up to enable air circulation
• Fridge/freezer – empty and clean, wedge doors open
• Interior – clean thoroughly heads, galley, cabins
• Key – leave with boatyard/marina/Island Dreams
• Linens – remove final items for laundering
• Locker/cabin doors and drawers – wedge open
• Perishable food, soda/fizzy drink cans & garbage – remove from boat
• Ports and hatches – cover to avoid sun damage to interior
• Water tanks – either top off and add water conditioner, or empty as appropriate
• Woodwork – clean with vinegar solution

In-Water Storage

• Chafe gear – add as appropriate
• Prop, shaft, rudder, bow thrusters – schedule cleaning as appropriate
• Zincs – check