Boats, whether large or small, whether sailing or cruising, should be insured. Cover can be provided to insure the full hull value including engine breakdown.
Liability cover should be purchased in case you cause damage or injury to third parties. If your boat is larger and has full time crew then consideration should be given to crew health and accident policies.
Insurance can be designed to cover local usage, regional sailing, global voyages, transportation on board container ships, racing and many other activities.