How to Winterize Your Boat

November 13, 2005
By WaterWing

Unfortunately, in many parts of North America we need to park our boats away for a few months of the year. Here are step-by-step instructions for winterizing your boat, insuring that, come May, it's just the way you left it in September!

1) Stabilizing the gas.
Adding the stabilizer will preserve your gas. Some think that draining the fuel is good. If you do that, the seals inside the fuel line can dry out and crack. Add the stabilizer to the gas tank and either add more gas or drive the trailer around to mix it up. Make sure the amount of treatment matches the amount of gas you have left (for example, 8oz treats 20 gallons). Some leave a half a tank so they can add fresh fuel in the spring and others believe a full tank is better to prevent condensation. You make a choice.

2) Clean the carb.
Remove the flame arrestor on top of the carb. Start the engine (with the garden hose connected). While the engine is warming up, clean the flame arrestor with carb cleaner. When the engine is hot, begin to clean the carb. Spray the carb cleaner all over the carb. Don’t flood the engine. Spray and let the engine burn some before spraying more. Don’t choke the carb with fogging oil yet… we’ll do that after the oil change. Turn off the engine and if applicable, remove and replace the water fuel separator.

3) Change oil
If your engine is newer, you will have a drain hose attached to the bottom of the oil pan. Feed the hose through the transom drain plug and open the oil drain (requires two wrenches). For the older models, you have to pump the oil from the dipstick. Pumps (that hook up to your drill) can be purchase at the local boat store. If you performed step 2, the oil will be hot and can easily be pumped out. Replace the oil filter. Some believe you should change the oil in the spring. If you are one of them, then change the oil now and again in the spring. Don’t let contaminated oil sit all winter.

4) Choke the Carb.
Start the engine again and immediately choke/flood the carb with fogging oil. The reason why we did this now is to let the new oil flow through the system (a Merc recommendation). Choking the carb with fogging oil lubricates the carb seals.

5) Drain engine water.
Out of all the steps listed, this is the most important… do it right! The newer engines have blue wing nuts that should be removed (for a v8 there 5). The older models have brass nuts usually located on the side of the block. If your engine doesn’t have a drain by the low part of the water-pump (in front of engine), then remove the water hose to drain. It's a good practice to stick a small wire in the block drain holes to remove any blockage. Replace all the drain plugs.

6) Apply anti-freeze.
This is an optional step. Many marinas don’t do this. However, if any water is left in the engine, the anti-freeze will mix with it. Also, it keeps the inside from corroding and the water pump lubricated. There are two ways to apply the anti-freeze.
1) Have it sucked up through the stern (kits can be purchase the local boat store)
2) pour the anti-freeze directly into the block.
If you suck the anti-freeze from the stern, the engine needs to run again and you should save step 4 until after this step.
I pour it directly into the block. At top and front of the engine, you will see water hoses connected to the block. Disconnect the water pump line (usually the fattest one) and use a funnel with a flexible hose to pour anti-freeze into the block. Use a rag to fill the gap between the funnel and the block opening to eliminate spillage. For a v8, this will take close to two gallons. Pour anti-freeze into the water pump hose to fill up the water pump. You can get the anti-freeze from the local boat store (make sure it’s the anti-freeze for the engine and not for plumbing water line). Some use auto anti-freeze, but this is not friendly to the environment so make sure in the spring the anti-freeze is drained before you start it (regardless of which anti-freeze you choose).

7) Fog each cylinder.
This is where you remove each spark plug and spray a healthy amount of fogging oil into each cylinder. An option step would be to turn the crank with a wrench (with the ignition off) to spread the fogging oil. Replace the spark plugs.

8) Change lower unit oil.
This is also a very critical step. With the trim in the down position, locate and remove the two drain screws. They are both located on the port side. The bottom one is between the skeg and the prop shaft. The top one is almost at the top of the stern and is marked as “vent”. If you have the lower unit reservoir tank, take off the cap. When all the lube has drained, use a pump (don’t try to use the squeeze tube… to messy) to replace the fluid. Attached the pump to the lowest drain (between the skeg and prop shaft) and begin pumping the new fluid in. Keep adding fluid until the top drain (marked as “vent”) begins to drain the new fluid. Place a new gasket on the drain plug screws and screw in the “vent” plug. If you have the lower unit reservoir tank, continue to pump (from the bottom) until you see fluid entering into the tank. Replace the lower drain plug screw (with it’s new gasket). Top off the reservoir tank and replace the cap.

9) Grease trailer,prop and outdrive
Grease the bearing buddies (if applicable), remove the prop and grease the prop shaft and the outdrive (look for the zerk fittings by the moving parts of the outdrive). Spray WD40 on all moving linkage parts on the engine.

10) Put the stern in down position and remove the battery
This one is self explanatory :-)

It's interesting to note, most marinas only perform steps 3,5 and 8 on this list.