Inspect Your Rigging
Getting to the water only to find a fitting has broken, a clevis ring is missing or a halyard is frayed can ruin a whole day. A visual inspection is easy and can generally be accomplished in a couple hours or less. All you need is a magnifying lens, a mirror, some toilet paper, your fingernails, a boatswain’s chair, and a pair of reasonably good eyes.
BoatU.S. article on Inspecting your Mast and Rigging.
BoatU.S. Rigging Checklist
How to Keep Your Jib Furler Alive, by Brian Toss
It's worth spending a little time to inspect and clean your deck hardware hardware when you lay your yacht up for the winter as this can save you money in the long run and prevent a future failure next season. Don't forget to also wash the boat thoroughly, dry and stow away non-essential halyards and sheets; they will last longer and will be clean for next season.
Below the surface of the water lives an environment that can be tough on a boat and its metal parts and fittings. Inspect and service these parts when the boat is out of the water, and perform visual inspections when cleaning or swimming on the bottom of your boat. Check all zincs annually, if half (or more) of a zinc has been lost to corrosion, replace it.
Sacrificial Anodes, by Don Casey
Inspect your propeller for any growth or visual damage. This will help improve performance and help maintain the value of your investment.
If you have an outboard you should check the propeller as part of your pre-launch routine. Use a deep well socket to make sure the propeller nut is secure.
You should also remove the propeller several times during the season to make sure discarded fishing line hasn’t become wrapped around the propeller shaft. If it has, have your dealer inspect the gear case, because fishing line can cause gear case leaks and gear case service is not a do-it-yourself job.
While you have the propeller off, inspect it for nicks, dents and other signs of damage. It’s OK if your prop is missing paint, but send it out for repairs if you find signs of impact. The smallest dent can cause your boat to lose 10% of performance and will burn more fuel than normal.
Finally, put a liberal amount of waterproof grease on the propeller shaft and re-install the propeller and hardware in the same order that you took them off, and tighten the propeller nut to the manufacturer’s specifications.