Boat Maintenance Tips For Winter

several boats under covers stored on trailers on brown gravel trackWe can all agree that preventative winter maintenance isn’t fun. As it signals the end on your boating season and time for some work to begin. You can hire a marine mechanic to “winterize” your boat to takes care of the big-ticket items, but it’s expensive. However, I like to save some cash by doings the simple tasks beforehand. To save you time, effort and money here are my boat maintenance tips for winter.

Why Do You Have To Winterize A Boat?

Boat owners up the North understand all to well the dangers of not winterizing their boats. Whereas Southern boats in areas like Florida, Texas or Louisiana, try to roll the dice. No matter where you park your boat in the off season, winterizing is vital to prevent freeze damage to your boat.

H20 Danger

By far the greatest danger of boat damage in winter comes from water. Due to the fact that water expands when it freezes. Water freezing is especially harmful in your engine system. No boater wants to find out in Spring their boat has a cracked engine block. So do yourself a favor and always winterize your boat.

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Table of Contents

Preparing Your Boat’s Engine For Winter:

First, check your owner’s manual of the boat and motor for manufacturer’s recommendations. If you are new to boat ownership use the help of a friend with experience in winterizing.

Inspect Fuel System

photo of person on dock filling fuel tank of white boat

Regardless of the engine type anyone can use an eye test on an engines fuel system. First, look for obvious signs of corrosion and leaks around the fuel system hoses. Doing this is particularly necessary for gasoline engines.

Some cheap fuel tank vent fittings use inferior materials, which promote early corrosion and failure. So pay close attention to the vent fittings as well as the actual hose and clamps. For any fittings that look blistered or deteriorated it’s best to replace them. The same goes for hoses with bulges or soft spots.

Top up your fuel tank to prevent a build up of condensation in the bottom of the tank throughout the winter months.

Next, add a fuel stabilizer to prevent phase separation and gum/varnish in gasoline. Diesel fuel stabilizers reduce the growth of bacteria that can clog injectors. After you deal with the fuel you can replace the fuel filters and water separators.

Next are specific maintenance tips for each engine type.

Outboard Engine(s)

person wrenching on outboard engine to complete boat maintenance tips for winter

  • Scrub the engine with soap and water. Rinse with fresh clean water.
  • Flush the engine with fresh water using flush muffs attached to the raw water pickup. Ensure you allow all the water to drain from the engine.
  • Disconnect the fuel hose and run the engine until it stops. It’s critical you follow a careful process to make sure all fuel gets drained out of the carburetor. This is important to prevent build-up of deposits from left over fuel. Once empty use a fogging oil to lubricate the cylinder walls and pistons in the carburetor. Fogging is vital to prevent corrosion in the fuel lines.
  • Inspect the propeller(s) and apply anti-fouling to prevent barnacle growth.
  • Apply a good water-resistant grease to the propeller shaft and threads.
  • Next, change the lower unit gear oil. Finish up by storing the outboard engine in the lowest position.

Inboard Engine(s)

main in striped shirt leaning over inboard boat engine

  • Start by flushing the engine with fresh water.
  • Next, run the engine until it warms up. Drain and change the oil while the engine is still warm. Draining oil from a warm engine pulls more impurities away with the oil. Don’t skip end of season oil changes. Leaving old oil in the crankcase can form acids, which corrode engine components. After changing the oil replace the oil filter as well.
  • Now you will want to change and fill the engine block with antifreeze. Use propylene-glycol antifreeze for long term boat storage. It’s best to ensure you also circulate antifreeze through the manifold. Do this by using the pickup hose via the water pump to a bucket of antifreeze. The process for this is to run the engine allowing for circulation until water exits the exhaust. This above process differs depending on if you have a raw water or enclosed fresh water cooling system.
  • Since you are changing fluids, also change the fluid in your transmission.
  • Moving on, change out the spark plugs and use “fogging oil” to spray into each cylinder.
    Wipe down the engine with a shop towel sprayed with a little fogging oil to finish up.

Stern Drive Engine(s)

  • For this type of boat engine, do a thorough inspection of the stern drive. Making sure to remove any vegetation or barnacles from the lower unit.
  • Next drain the gear case, as you do it look for excessive moisture in the oil. Seeing moisture in the oil could mean leaking seals, get them repaired or replaced.
  • Or if you find no moisture move to cleaning the lower unit with soap and warm water.
  • For stern drives with a rubber boot, inspect it for cracks or pinholes.Now, grease all fittings and check the fluid levels in hydraulic steering or lift pumps. Top up these fluids as needed.

Finish up the engine section by ensuring you complete any added recommendations by the engine manufacturer.

Maintain The Bilges

Before storing your boat ensure you clean the bilges, and they are dry. To clean dirty bilges you should use soap, hot water and a stiff brush to tidy up all oil spills. After cleaning, spray with a moisture displacing lubricant. Finally, a good idea I like to do is to put a little antifreeze inside to prevent any water you miss from freezing.

Inspect Your Boat’s Electrical System

Beyond looking at the wires in your engine, it’s important to do a visual check of the electrical wires for your boat. Follow the wiring and fix any corroded connections. Also make sure terminal blocks, screws and fuses are corrosion-free. Test the all the navigation lights for function. Remove the bulbs from your navigation and running lights. Then spray the exposed sockets with an anti-corrosion lubricant.

Isolated photo of black battery with red and black cables attached to terminals

What kind of condition are your batteries in? Check the charge levels followed by making sure to clean and tighten the terminals. If you don’t use an onboard battery charger this is the time to remove the batteries. If you use lead acid batteries, top up the electrolyte levels and recharge. For AGM, Gel or lithium put your batteries on a marine smart trickle charger.

Related: Best 2-bank Marine Battery Charger (2020 Reviews)


Winterizing Potable Water System & Sanitary System

Like your boat’s engine, other systems that use water need protection from freeze damage. Below are basic ways to winterize the freshwater system and sanitary system inside the vessel.

Fresh Water System

Be sure to completely drain the freshwater tank and hot water tank. Pump non-toxic antifreeze through the potable water lines. As you do, turn on all faucets and the shower. Keep pumping until antifreeze comes out of all opening, then close the faucets and show.

Sanitary System or Marine Head

photo of a head and sink/shower combo in a boat

Any water left in your boat’s sanitation system could freeze and cause terrible damage. First pump out your holding tank at a marina. As you pump it out, replenish the bowl with fresh water and flush many times. Use a product your owners manual recommends for cleaning as you pump fresh water. After a few minutes, add some antifreeze to the bowl. Pump it until its through all hoses/valves, the holding tank, macerator and discharge hose.

Exterior Boat Maintenance Tips For Winter

To begin the exterior boat maintenance tips for winter, focus on the hull and topsides of the vessel. The method you choose will depend on how you plan to store your boat, either out or in the water. Below are some tips for each type of storage:

Out-Of-Water Winter Storage

Start by pressure washing the hull, ensure you clean of any barnacles. Pay specific attention to the props and shafts, rudders, struts and trim tabs. Clean all thru-hulls and strainers. Open the seacocks to allow any stored up water to drain. Evaluate the hull for any blisters, if there are any, fix or open them to drain over the winter.

white boat with teal cover docked out of water on a lift

Now it’s time for a complete wash down of the boat. Remove rust stains, tree sap and water stains from the topsides and hull. Don’t skip this process as these stains can become permanent by spring. Next, give the hull and topsides a thorough wax and compound treatment. This helps to prevent oxidation and UV damage.

Boat-In-Water Winter Storage

For keeping your boat in the water over winter do the following. Make sure to close all the seacock valves. Next check the rudder shafts and stuffing boxes for leaks. If you find small leakage simply tighten or repack as needed.

Moving on, inspect the dock lines for strain damage. Replace or add chafing gear to the line to prepare for impeding winter storms. For boaters in area where the water is prone to actually freeze, consider installing a de-icer. This can help prevent ice forming against the hull which may lead to “ice jacking” that can tear through the hull. Last but not least, check the boat on a regular basis or have the marina complete this and report back to you.

Exterior Protection: Boat Covers Or Shrinkwrap

The method you use for protecting the exterior of your vessel comes down to personal preference. Both options offer adequate protection from the elements, but which to choose is up to you.

Shrink Wrap

snow covered shrink wrapped boats

This type of cover ranges in price and install quality. Owners tend to hire professionals to install it own their boats. Shrink wrap does provide waterproof protection but its non-breathable. If moisture gets under the wrap it may cause damage such as mildew up to rot damage.

Canvas Boat Covers

Most boaters know the biggest advantage of using a boat cover is they can reuse it season after season. The downside is covers are more expensive than a single shrink wrapping session. But any good quality boat cover will protect the boat from the elements for seasons to come.

Another bonus is they’re made of breathable materials like canvas. This allows for air flow which helps trapped moisture escape. Plus you can access the interior of the boat throughout the season to check up on it.

Winterizing Props

Now take a look at the props on your boat. Determine if they need repair or only need a good cleaning. Prop maintenance is a perfect DIY off-season job for boaters of any experience level.

If your props have chips or damage send them off for repair and have them delivered back early or mid-spring. This saves time and avoids last-minute issues, such as confirming with a professional if the prop needs replacing.
However, if the props just need cleaning, apply many coats of anti-fouling cleaner. This reduces the potential growth of barnacles, in both freshwater and saltwater. Props that are free of foreign growth increase their ability to operate at maximum performance.

Interior Boat Maintenance Tips For Winter

  • First, remove all loose items and valuables from the vessel and pack them up in labeled storage boxes. I like doing this for easy unpacking in Spring.
  • Next clean out the refrigerator/freezer to reduce mold and mildew issues. To ensure easy operation next season oil all doors and hinges.

photo inside a blue and white colored boat cabin on rainy day

  • Now move on to the actual cabin of the boat. Pay special attention to controlling humidity inside this area during storage. Keep the interior of the vessel ventilated, with either active or passive vents. An example of an active vent is a battery powered day/night vent. Whereas passive vents includes cowl, clam-shell or louvered vents.
  • Another option is to add a low-temp heater or a “no-damp dehumidifiers in the engine room. For even cheaper, you could try moisture absorbing crystals to cut mold and mildew inside.
  • Next, vacuum all the cushions/mattresses and store them in an upright position. This aids in good airflow for storage.
  • For boats with canvas tops or enclosures, ensure to lubricate all snaps and zippers. This is important to do whether you leave them installed over the winter or not.

In Conclusion: Boat Maintenance Tips For Winter

As of now you have a complete idea of what to complete to ensure your prized boat is safe and ready for winter storage. For new boaters, feel free to hire a professional marine mechanic. Or if you prefer to do-it-yourself get an experienced buddy to help. Those of you with experience can use these tips as a reminder of the importance of good boat maintenance.

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