We have a long list of items to take care of when leaving the boat for an extended period.
You can either run the engine
about once a month or do the winterization as mentioned in the engine manual. A lot depends on whether it will be freezing where your boat is.
Do take care of the batteries, you will need them for starting the engine. With good batteries you should not have problems if you run the engine once a month. But run the engine long enough to recharge the battery
(might be about an hour, depending on the state of your battery).
Keep the fuel tanks
full, to prevent condensation
Empty the water tanks
will go foul over that period. If there is a danger
of freezing, also blow through all fresh water systems, to empty all hoses etc.
Toilet water might start smelling bad as well, flush it whenever you have a chance, unless you winterized it as well.
Close all hatches! that prevents water ingress during heavy rain. But have all dorades or whatever ventilation system you have open. To further prevent mold
, remove all cushions
and matresses and open all enclosed spaces and lockers, even the bilge
And remove all food
, that is not in tins or glass. Helps keep the crawlers out.