How To De-Winterize A Boat And De-Fog An Outboard
9 essential maintenance steps for preparing your boat for the summer season.
April 25, 2024
As summer approaches, boat owners begin the essential spring task of preparing their vessels for the water after a long winter. De-winterizing your boat and de-fogging an outboard engine are critical steps to ensure your boating season is both safe and enjoyable. Here's a comprehensive guide to get you started.
Step 1: Remove Shrink Wrap Carefully
Begin by removing the shrink wrap or protective sheeting that you used when winterizing your boat to provide protection from pests, dust, and grime during the off-season. This is a crucial first step before you start inspecting and servicing various components of the boat. Do so with care to avoid damaging any gelcoat or paint. Once removed, get a hose and rinse down and clean the boat to get her ready for the season.
Step 2: Check Engine
Above: A man de-winterizing his outboard engine, burning off the fogging oil before his first boating trip of the spring season. Image created using OpenAI's DALL-E.
The first and more important thing to check when de-winterizing a boat for the season is the engine (or engines plural for those with multiple engines). Below is a list of the most important engine maintenance steps for spring commissioning a boat:
- Check Fuel Lines - Before doing anything, inspect the engine and all fuel lines for signs of corrosion or leaks before starting. If you find a leak, it is important to repair it before starting the motor. Do NOT start an engine that has been sitting with fuel in the lines and tank without first properly ventilating the engine compartment and the surrounding area (inboard engines generally have a blower fan for this), or you may risk an explosion.
- Check/Replace Water Pump, Impeller and Thermostat - Inspect and possibly change the water pump impeller, which is the essential internal rubber part inside the water pump necessary for cooling the engine by pumping raw water through the motor at varying speeds. As a general rule of thumb, it is wise to replace the impeller every other year, and more if it sees a lot of use. The thermostat should also be checked and replaced, especially if it has reached 200 hours of use, to ensure the engine maintains the correct temperature.
- Fill With Fresh Gas - It's best to run fresh gas if possible for your first trip out to ensure the fuel system hasn't been contaminated with moisture or water. Be sure to add the correct amount of marine oil additive for two-stroke engines if applicable.
- Starting & De-fogging An Outboard Engine - If you fogged your outboard engine during winter storage (which you should do btw, see our Boat Winterization Guide), you'll want to start by burning off the excess fogging oil. Warming up the engine on muffs or in a water bucket in your driveway or yard, or at your local ramp, is recommended. Allow the fogging oil to burn off completely, which might take between 5 to 10 minutes or longer depending on the amount used and whether or not it was also added to the fuel system. Once the engine is sufficiently warm and the fogging oil has burned off, you can replace the old spark plugs with new ones.
- Replace Filters - For boats with four-stroke or oil-injected two-stroke outboard engines, check and replace the oil and oil filter. Then clean and/or replace your fuel filter(s) and ensure you have a fresh tanks of gas. We put this step last, since you may want to burn of the fogging oil completely before putting on new filters—especially if you or your boat shop added any fogging oil and Marvel Mystery oil additive to the fuel.
Step 3: Check Cooling System
For boats with an enclosed cooling system:
- Check the coolant and water mix, ensuring it is clean and at the correct level.
- Inspect the system’s hoses for holes or cracks.
- Optional: Drain and refill the system to the proper levels.
NOTE: For air-cooled and raw water-cooled outboard engines, the above steps likely do not apply, however you should ensure the rubber water pump impeller is not cracked and functioning properly.
Step 4: Check The Bilge And Drain Plug
Next, check and clean your bilge system. Your boat's bilge pump is a vital component for safe operation of the vessel. Make sure it is pumping the right amount of water and there are no obstructions or leaks anywhere. A clogged bilge pump is a safety issues as it could lead to the boat getting "swamped" and overwhelmed with water, increasing its weight, threatening its buoyancy and becoming waterlogged. Also check the bilge pumps automatic switch to ensure it is activating when it reaches the appropriate level. And, while your at it, check that your boat's main drain plug(s) is/are securely attached and in place.
Step 5: Cables, Hoses, and Belts
Check all cables and hoses for wear and secure them tightly. Take care to inspect all soft rubber parts, including coolant hoses for any damage. Belts should have minimal give when pressed; replace any that appear worn or show soot near the pulleys.
Step 6: Battery Maintenance And Test
Test your boat battery’s volts and amps with a battery tester to ensure it can hold a charge. Top off any fluids with distilled water and clean any corrosion from the terminals.
Step 7: Fuel System Inspection
Inspect the entire fuel system boat-wide (for boats with in-hull tanks) to be sure the fuel lines and fittings aren't leaking anywhere in the boat and causing potentially dangerous vapors and fumes to build up anywhere. Check for cracks and replace the fuel filter if it was not changed last season. Drain any old gas in the tank if possible, especially if no additive was used, to prevent fuel separation or water contamination (as mentioned earlier).
Step 8: Exterior Hull Check
Check the boat’s exterior hull for any damage like cracks or missing hardware pieces. Inspect the scuppers, transom, hardware mounts (depth finder, etc.) and hull sides around the entire vessel. The last thing you want to do is launch a boat into the water that has a leak and immediately starts taking on water.
Step 9: Safety Gear and Clean Up
Verify that all safety equipment is up to date and functional. This includes fire extinguishers, lights, signaling equipment, and flotation devices for all passengers. Finally, ensure all electronics are functioning, charge the battery, check navigational lights, and give your boat a final clean-up.
Above: A woman enjoying a sunny day on a boat. Photo by Timothy Yiadom.
Ready For The Water!
Taking these steps will help ensure your boat is ready for a successful and enjoyable boating season. Remember, regular maintenance not only extends the life of your boat but also enhances your safety on the water. If you're uncertain about any procedures, consulting a boating expert or professional mechanic is always a good practice. Happy boating!
