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Rainfall of six to 12 inches in 24 hours is common during a hurricane, and as much as two feet can fall in a day! Cockpit scuppers can be overwhelmed by such torrents, and even boats stored ashore can suffer damage if rainwater overflows into the cabin. Boats stored in the water can be sunk when rainwater backs up in the cockpit and the weight forces deck drains underwater, causing them to backflow.
Make certain cockpit drains are free-running. If your boat is staying in the water, remove heavy items from the stern area, such as anchors, extra fuel tanks, and kicker motors, so that the cockpit scuppers are higher above the water. Close all but cockpit drain seacocks and plug the engine’s exhaust port. Use masking or duct tape to seal around hatches, ports, and lockers to keep water from getting below. Seal exposed electronics. Make sure the bilge pump and switch work, and that the battery is topped up; shore power is not likely to remain on throughout the storm. Keep in mind that the ability of the pump and battery to remove water is usually greatly overestimated. Small boats should be covered if possible.
Waves make boats bounce in their slips, displacing fenders and increasing strain on docklines. Double up on docklines and make sure all are well-protected from chafe. While fenders and fender boards won’t compensate for poor docking arrangements, if the boat is well-secured, they may offer some additional protection, especially if they are heavy duty. Smaller boats can be overwhelmed, especially if they are stern-to to the waves. The bow is strongest and least likely to be overcome by water and should face into the waves..
On a fixed dock, a boat will rise as much as 10 feet or more and it must be tied loosely enough to allow it to rise, but not so loose that it bangs against the dock. Long lines taken to an adjoining dock or piling and long spring lines will allow the boat to move up and down while still holding it in position. Floating docks rise with the surge, but if it’s high enough, the surge can float the docks right off the pilings.
“The time for taking all measures for a ship’s safety is while still able to do so. Nothing is more dangerous than for a seaman to be grudging in taking precautions lest they turn out to have been unnecessary. Safety at sea for a thousand years has depended on exactly the opposite philosophy.”
ADMIRAL CHESTER W. NIMITZ