How to Dewinterize a Boat

Winterizing a boat involves the precautionary measures to insure that systems and components will last through the winter without damage. Rust and corrosion, caused by weather, negatively affect vital components that rely upon proper lubrication. Dewinterizing a boat involves the process of getting a boat and engine ready for a season of use after a long shutdown. Dewinterizing properly insures the boat has received no temporary or permanent damage during the storage interval, which can lead to poor performance and sometimes a no-start condition.

Remove any tarp of covering from the boat. Inspect the inside deck and bilge area for twigs, grass, leaves and any foreign debris. Use a whisk broom to clean decks and bilge area and bag the refuge in garbage bags. Mop up any puddles or standing water in the bilge area with towels. Use some bleach and a wet towel to clean any mold or algae that has collected in the bilge or interior hull sides. Use a socket and wrench to screw in the bilge drain plug.

Replace any items in the boat that were removed for winterizing, such as life vests, seats, flares and fire extinguishers, first aid kit, coolers, fishing tackle and tools. Make sure none of your safety gear components or first-aid supplies have expired — replace them, if necessary. Remove the battery caps if you have a starter or auxiliary battery and replace any battery water with distilled water up to the proper level. Use a hydrometer to check the charge rate. Use a battery charger to bring the battery up to full charge, if low.

Use a socket and wrench to remove both battery cables. Clean the battery terminal posts and cables with a wire brush. Reinstall the cables and tighten them with a socket. Reinstall any radio, fish finder, GPS locator and any other electronic devise. Turn on your main power switch and check each component for operation, including the horn and running lights.

Install the outboard motor or trolling motor, if you have removed one. Connect any electrical wiring harness to the engine. Test the steering wheel or tiller response, making sure the engine turns smoothly left and right to its full range. Connect the quick-release fuel line hose from the tank to the engine. If you have removed all gas from the tank, fill the tank with fresh fuel to the top. Check the fuel primer bulb for cracks.


Unclasp the engine cowl snaps or remove the engine case cover (stern-drive). Remove the plug or plug wires from the engine, then use a socket to remove each spark plug. Check each spark plug for the proper gap with a feeler gauge, according to your owner's manual specifications. Clean the spark plug electrodes with a wire brush then screw them back into the cylinder heads with a socket. Use a socket to remove the gear case oil plug and check the level — add as necessary.