How to Winterize a Boat Engine

How to Winterize a Boat Engine

The cold months of winter can wreak havoc on your boat’s engine if you don’t properly prepare it beforehand.

For most people, the thought of winterizing their boat engine seems daunting at best, impossible at worst. However, it doesn’t have to be.

To protect yours, follow these simple steps on how to winterize a boat engine.

How to Winterize a Boat Engine

Tools and Materials Needed

  • Engine coolant
  • Lubricant
  • Oil pump
  • Fuel stabilizer
  • Flush muffs
  • Engine fogging oil
  • Oil filters
  • O-rings
  • Oil drain pan
  • Grease gun

Step 1 – Add Stabilizer and Top-up Fuel Tank

Before storing your boat, the first step is fully topping off the fuel tank and adding a fuel stabilizer.

Topping off your tank can help prevent condensation buildup, resulting in rust damage or fuel contamination if left unattended.

On the other hand, adding a fuel stabilizer will prevent your fuel from turning into sludge during freezing temperatures. Sludgy fuel can cause expensive damage to your engine.

Follow manufacturer instructions to determine how much stabilizer you require for your type of fuel and engine size.

Step 2 – Flush with Flush Muffs to Warm the Engine

Attach flush muffs (also known as earmuffs) to the water sports on the lower end of your motor. Next, turn the water on and allow the engine to run for 5 minutes.

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Running the engine prevents condensation from forming inside your motor, reducing damage.

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Step 3 – Drain Water from Engine Block

Start by removing any plugs from your water pump or cooling system. Next, drain as much fluid from your engine block as possible (you can use a bucket or place hoses into an open bucket).

Step 4 – Flush with Antifreeze

After you have drained all the water, add antifreeze into the cooling system until it’s about half full.

Antifreeze for boat engines comes in different forms, such as ethylene glycol or propylene glycol.

Consult your boat engine manual for details on which antifreeze is appropriate. Make sure you use antifreeze explicitly designed for marine applications.

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Step 5 – Fog the Carburetor and Combustion Chamber

Fogging your carburetor and combustion chamber will help prevent corrosion from forming during storage.

To fog, a carburetor first drains out the gas tank, removes the air filter, and finally, the spark plugs.

Next, spray your engine fogging oil into each cylinder, and run (rather than idling) the engine until it can expel all of the solvents.

Be sure to follow all safety precautions, as solvents are flammable.

Similarly, remove all spark plugs and spray fogging oil into each hole to fog the combustion chamber.

Let the solvent soak for several minutes, then start your engine while holding down on an exhaust manifold. Once again, follow all safety precautions.

Step 6 – Drain the Gear Oil

To drain the gear oil, first, unscrew the lower drain cap on the boat motor’s lower end, followed by the upper drain cap.

Once all the caps are out, pour your gear oil down an appropriate drain. Other boat engines come with dipsticks and require that you remove your dipstick.

Step 7 – Change O-rings, Oil Filter, and Water Separator

Check O-rings, oil filter, and water separator (if equipped) for signs of corrosion or damage.

Change all three of these items if they are in poor condition, have indications of rust, or are damaged.

If you have a water separator, change its element and clean them at least once per season.

Follow manufacturer’s instructions for replacement steps. Remember to test all parts for leaks after installation and before launch.

Step 8 – Pump Fresh Oil Back

After you’ve drained and flushed your engine, it’s time to refill it with clean, fresh oil.

Attach a suction pump to the lower oil drain cap on the bottom of your motor (or a dipstick tube) and start pumping new oil back into your crankcase

Pump several times until no more air bubbles come out. Lastly, close off all hoses and fill caps firmly but gently so that no air bubbles are trapped inside.

Step 9 – Lubricate All the Engine Components

When performing lubrication, you’ll want to use marine-grade grease found in major online retailers or a marine supply store near you.

Ensure to grease all of the engine components. These include propeller shaft and hub, engine belts, shift linkages, stern tube seals, any bearing surfaces that could contact water.

Step 10 – Disconnect the Battery

Before putting your boat in storage, the final step is to disconnect your battery.

To avoid having problems with corrosion or dead batteries,

detach your power cable from one terminal on each of your batteries while they’re still warm (the warmth will help prevent rusting).

Next, clean off all dirt and debris that might have accumulated on the surface of each battery terminal and cover them with petroleum jelly,

so no water gets inside while they sit over winter break.

Final Step

Once you have disconnected the battery, it’s time to take action on storage.

Depending on where you live, getting your boat ready for winter could be as simple as parking it in an indoor storage lot.

When storing your boat outside, you can cover it with a tarp or throw some carpet over it to keep water from damaging or degrading the deck.

Also, remember to apply at least 4-6 coats of wax to protect your finish from snow and rain.

What happens if you don’t winterize the boat engine?

Not winterizing your boat can be detrimental, as extreme temperatures cause damage that’s not easily repaired.

Therefore, it’s essential to clean and winterize your engine before every harsh season.

Here are some common problems you might encounter if you don’t properly care for your engine:

1.    Corrosion

When saltwater freezes, it expands and corrode metal parts within seconds. If you neglect cleaning and protecting your vessel during cold weather,

you could end up with a giant hole in your hull or other structural damage that requires costly repairs or replacement.

2.    Idle loss

Cold weather causes fuel and oil to separate, which means gasoline left sitting for long periods will freeze instead of evaporating out into the air.

As a result, it causes so-called idle loss. When gas leaks from engines because owners aren’t running them enough to keep their fuel fresh

3.    Reduced horsepower

An engine kept in a warm garage, or covered area won’t need lubricating oil to stay warm.

During the summer months, the uncovered engine still gets hot from operating frequently. Cooler fall temperatures lead to coolant loss through evaporation.

As grease and oil get thick, friction decreases, leading to slower acceleration and reduced horsepower.

It’s always advisable to take extra precautions with your boat. Think about winterizing other parts,

such as lines and fenders that aren’t stored inside (note: you will have to remove these from time to time during the summer months).

Moreover, if there are items on your boat that you leave outside year-round, consider finding a place to stow them away when not in use.

It ensures they stay functional and safe for next summer.

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