The Ultimate Pre-Winter Preparedness Guide - For Boats


It’s the start of the winter storage season. Now is the time to make plans and prepare your vessel for the cold months ahead. 

What Is Winterizing?

Winterizing is a process that prepares your watercraft for freezing temperatures. It is typically carried out in the fall, before excessive cold temperatures and harsh weather conditions arrive. 

When water freezes, it expands as it becomes ice. This expansion can cause significant damage to a boat’s engine and other systems – such as a cracked engine block, damaged fiberglass, split hoses, and more.

Unfortunately, these issues can result in expensive, tedious repairs - especially if there is freeze damage found in the engine or cooling system. 

Winterization can protect the watercraft against such damage. It involves draining all water onboard and replacing it with an antifreeze solution instead. This can help protect the boat against freezing temperatures during the winter months.

» MORE: Winterize Your Boat for the Off-Season 

What is Antifreeze? 

Antifreeze is a liquid-based solution that helps to lower freezing points.

There are different types of antifreeze additives that can impact the freezing temperature. The antifreeze you put in your engine and plumbing systems should have the proper freeze protection needed to keep the systems safe and working properly. 

Additionally, antifreeze that’s used for winterizing engines and freshwater systems is different from the coolant you put in the engine’s heat exchanger. Ethylene glycol, for example, is commonly used as a coolant. It is highly toxic and should not be used to winterize drinking water and raw water systems. Propylene glycol, on the other hand, is safe to use and doesn't have a taste. 

Should I Winterize My Boat?

Those who do not winterize or do not properly winterize, could stumble upon damage in the spring when preparing to launch their boat. Repairing freeze damage is time-consuming and could even entail a complete engine replacement. By the time the vessel and its systems are finally working correctly, the season could be over. 

Even if you live in an area where temperatures typically remain mild during the winter, your vessel is still vulnerable to freeze damage. There is no way to accurately predict how cold the winter will be in your state. It’s always better to be over-prepared and underwhelmed than underprepared and overwhelmed. 

Preparing for Winterization

It’s easy to miss a step while winterizing. Follow a checklist and the guidelines given. Mark each step off as you complete them to guard against unwanted surprises when springtime rolls around. 

You will also want to complete a pre-winterization inspection. First, take inventory of the boat’s fenders, dock lines, cushions, covers, and other equipment. Second, review and note the boat's current condition. Finally, thoroughly ??examine all electrical and mechanical systems onboard and take note of any issues. 

Steps for Winterizing Watercraft

  1. Change engine oil & filters (including fuel) 
  2. Change engine coolant 
  3. Check & adjust belts 
  4. Pressure test the cooling system 
  5. Change transmission fluid & filter 
  6. Winterize the freshwater system and all appliances 
  7. Winterize head, including the holding tank   
  8. Pump the holding tank 
  9. Disconnect cables and clean all battery terminals 
  10. Winterize refrigeration 
  11. Winterize air conditioning 
  12. Winterize saltwater wash-down pump 
  13. Inspect and clean shower sump and filter 
  14. Examine discharge pump and filter 
  15. Remove exterior cushions and canvas

» MORE: A Guide to Winterization

How To Winterize the Engine

Engines tend to be most susceptible to damage from freezing weather. As a result, the engine should be your winterization priority. 

For the most part, winterizing an engine largely involves draining all water and replacing it with an antifreeze solution. Here is a more detailed explanation of that process. 

  • Step 1: Prepare the inboard motor for winterization  

Fill the tank with gas to decrease the chance of getting air in it, add a fuel stabilizer to prevent buildup, and finally warm the engine. 

  • Step 2: Apply antifreeze

After the motor is cleaned and prepped, you can start to add antifreeze to the engine block and sterndrive. This will prevent any water or condensation from freezing, expanding, and causing cracks. 

  • Step 3: Fog the engine 

After applying antifreeze to the engine, follow up with fogging oil. Spray a generous amount with the engine running. Keep in mind - engines with low horsepower may stall out, while high horsepower engines may sputter. That’s perfectly normal - continue with the process. 

  • Step 4: Change the engine’s oil and replace the oil filter  

Your engine and transmission oil could be contaminated with dirt and other particles. This can cause damage while the boat is stored if not properly addressed. 

It’s best to complete this step while the engine is already warm. You should also start the engine and check the fuel filter for leaks. If one is found, turn off the engine and complete any necessary repairs. 

  • Step 5: Final inspection 

Complete a final check - inspect the exhaust system, check the hoses and hose clamps, and seal off any openings.

Freeze Insurance Coverage

Consider adding freezing coverage to your boat insurance policy. It’s generally an inexpensive addition and can protect you from a large repair bill down the road. This type of coverage still requires you to winterize your boat.  

Discounts for Winter Layup

At SkiSafe, we offer a generous winter layout discount. It’s designed to help boaters in places with mid-to long-term winters. This discount enables you to maintain sufficient coverage both on and off the water, protecting against theft and other covered losses even when your boat is not in use.  

» MORE: Winter Layup Boat Insurance Discounts

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