Skip to main content
Free U.S. Shipping on orders of $25+ 4 and a half star review rating


swell wakesurf winterization for dummies direct drive engine

Boat Winterization for Dummies

September 28, 2022      · 

Written by Adam Moore

Boat Winterization for Dummies

Back to school for a lot of us means the end of boating season. There are a lot of questions out there about winterization, so I wanted to share some best practices on what to do to prepare your boat for the off season. This isn’t necessarily a by the book maintenance program, this is what I’ve been doing my whole boating life and what has worked for me without issues for the past 42 years of my life. 

Whether you are in California, Texas, or Minnesota (like me), it is always safest to winterize your boat if you won’t be using it. You never know when a cold spell may come. If you follow the steps below, you’ll always be ready to go when boating season kicks back up!

Step 1: Stabilize your fuel

If you keep your boat on a lift during the season, the easiest way to stabilize your gas is on the lift before you head to the launch to take your boat out of the lake. Don’t worry too much about the exact right amount of stabilizer for the amount of gas in your tank. Just measure how much stabilizer based on a full tank and add it to your tank.

If your boat is on a trailer, head to the local gas station and fill up your tank. Get Non-Oxy premium, if possible, if not, we’d recommend the highest octane you can find. Filling the tank completely ensures that condensation will not build up during the off-season adding moisture to your tank. Add Seafom or fuel stabilizer. Adding it before trailering or driving to the launch will give the Sea Foam the opportunity to mix well in the tank. 

With a full tank of treated gas, the next step is getting the maintenance done. We always like to do this in the fall so when the ice is out in the spring, we can toss our wetsuits on and hit the lake with no delay! 

youtube play

Step 2: Mandatory winter maintenance 

The things we do every fall no matter what are: change the oil and filter, replace the engine impeller, and replace ballast impellers. 

Oil Change

A fresh oil change is a no-brainer, always good to store it with fresh oil to ensure any contaminants are gone. I will also do this every 50 hours like the maintenance manual recommends. Wake Surfing is constant higher rpms, which is extra tough on engines, and that is almost all we do. Get a transfer pump and learn to do it on the dock, it’ll ensure you long engine life! 

Engine Impeller Replacement

There is some disagreement on the engine impeller, you will hear a lot of people online say to only do this in the spring as sitting in the water pump will damage it, or that it isn’t needed every season, just inspect it, and ensure it is in good shape. My preference is to swap it out every season in the fall, we’ve been doing this for 40 years without issues on inboard boats, as far as it not needing it every fall, we just don’t want to have to deal with maintenance in the middle of the season, summers in MN are short and I want to the boat to have no issues all summer, my goal is to not have to do anything but ride!

Ballast Impeller Replacement

Most modern wake boats now have reversible ballast pumps, typically black pumps with brass heads, inside that brass head is an impeller. They look like this: 

two way johnson talulah ballast pump 13.5 gpm swell wakesurf

We do the same for these impellers, replace them every fall and you don’t have to do anything in the summer. You see the trend here! 

If you have an older boat that has a ballast system, it may have bilge style ballast pumps like these: 

shurflo piranha ballast and aerator pump swell wakesurf

One mounted on the thru hull for filling, and another on the tank or ballast bag for draining. These pumps do not have impellers and do not need service. 

Step 3: Additional checks

Fuel Filter & Fuel Water Separator

The next thing to check is your fuel filter and fuel/water separator if you have one. Most manuals will say to replace these filters every 50 hours. We usually use our boat 70-90 hours a season and do this in the fall with our oil change. 

Transmission Fluid

I replace the transmission fluid once a season in the fall as well. The easiest way we have found to do this is with an extraction pump like the one above we used for the oil change, we pump it out and then fill to spec. If your transmission does have a filter, they usually don’t require maintenance, but check your manual to be sure.

V-Drive Fluid

If you have a V-drive boat you will also have V-Drive fluid. I do the same thing here with the extractor, suck it out and replace it with the manufacturer recommended oil.

Raw Water Strainer

Most boats since the 2000s will also have a raw water strainer, they look like this: 

sherwood raw water strainer swell wakesurf

To service pull off the clear cover, drain the water, and clean the metal filter and reassemble. 

Step 4: Winterization


Winterizing your boat can be a scary thing for a lot of people but leaving water in the engine can be catastrophic to your engine and next boating season. I’ll take some of the scariness out of the process and walk you through the steps to ensure you don’t have any issues. 

When winterizing inboard engines, I’ve always liked to leave them full of RV antifreeze for the off season it provides protection that if there was a little bit of water left somewhere. It also ensures the empty engine doesn’t corrode. RV antifreeze is marine safe, meaning there is no delay to boating in the spring, you can just drop it in the water with no prep. 

Flush the heating system

If your boat has a heater, like most of our boats here in MN, then your boat will require some extra care. The system needs to be flushed to keep it from cracking, a lesson I learned the hard way.

On the engine there will be two smaller hoses, usually an inch diameter, that run off the manifolds back towards the bow, these are your heater supply and return, unhook them both and blow air thru them until the water no longer comes out, don’t use a compressor, high pressure can damage them, we typically use a high-volume pump that we fill our towable tubes and inflatables with. Once the water is gone reconnect the hoses.

Drain the engine

The next thing we like to do is drain the water from the engine. Some newer engines have drain plugs, you can check the engine manual, find them, and pop them out to drain the block. We typically just remove the hoses from the engine and water pump and allow them to drain. Once drained, hook back up the hoses or re-insert plugs and make sure all the clamps are tight.

Flush the cold-water intake with antifreeze

To further protect the engine, we want to get antifreeze fully into the engine block. I’ll walk you through the different ways I’ve done it and tell you which is my favorite method. 

Option 1 is to pull off the hose at your main thru hull location (where the engine gets water from the lake) open 3-4 gallons of antifreeze and have them ready to go. Start the engine and pour the antifreeze into the hose using a funnel. Once antifreeze is coming out of the exhaust shut down the engine and reconnect the hose. 

Option 2 is almost the same, but instead of pulling off the inlet hose, you can use a “Fake-A-Lake” style engine flusher attached to the water intake on the bottom of the hull. Start the engine and pour the antifreeze into the flusher, the engine will suck it up and once it comes out of the exhaust, you’re good to go. The only downfall to this is it does waste a bit of antifreeze as it spills around the fake-a-lake. 

seachoice fake-a-lake style engine flusher

Option 3 is my preferred method but requires an investment in a few parts. We winterize a lot of boats, and this has been the easiest for us. Remove the inlet hose and attach it to a garden hose with an adapter, the garden hose is then attached to a sump pump in a large plastic tub (20 gallon size or larger) with 3 – 5 gallons of antifreeze. Start the engine and turn on the sump pump, the pump will fill up the engine with antifreeze, the tub of is placed under the exhaust to catch the antifreeze and we let that cycle for a few minutes and shut down the engine.

sump pump in tub for antifreeze boat winterization

Flushing the ballast system

The last thing to winterize is your ballast system. Hit the drain on your pumps and ensure all the water is out of the system. Once that is complete put half a gallon of antifreeze in each bag/tank and then hit drain again to push it through the system. There are a few ways to get the antifreeze into the system, you can use a funnel and pour it down the ballast vents (modern boats with reversible pumps will have a check valve on the ballast vent, so make sure the antifreeze is getting into the system) or remove a hose/connection and dump it in. 


The last step is to fully charge the battery/s. Once charged, unhook the battery leads to keep them from being drained over the winter. I’ve had good luck with this, and the batteries have lasted their normal life, even in MN where it often reaches 20 degrees below zero. Another good option is to pull out the batteries and trickle charge them over the winter. 

Other considerations

Depending on where your boats winter resting place is, another thing to think about is rodents and moisture. 

If you store your boat covered with your standard boat cover indoors, I recommend a few dryer sheets in the boat (mice hate them) and a container of damp rid under the cover. The damp rid will reduce any remaining moisture that may be under the cover and ensure you have a dry boat come spring. 

If you store your boat outside, I would do the same thing with dryer sheets and damp rid, and I also highly recommend you get your boat shrink wrapped by a professional. This will ensure that any snow load will stay off your boat and it’ll be safe and dry outside. They add vents to the shrink wrap to allow air movement to keep the boat dry, normal boat covers do not breath as well and absorb moisture. This can cause issues come spring. 


Now that we have gone through what boat winterization is you should have a better understanding of the different tasks and hopefully even feel comfortable enough try some of them yourself. 

If you are looking for more information on winterizing your boat you can read this more in-depth winterization article with a video further explaining what you need to do.

At SWELL Wakesurf, we are passionate about helping you find the best setup for your boat. You can check our more informational articles and videos on our SWELL Content Page. If you still have questions, don’t hesitate to send us a message on our chat, send us a question at our help desk, or email at

SWELL Wakesurf Upgrade Division

Have us upgrade your boat for you. We can add or upgrade your tower, design and install a ballast system, bring your audio system to the next level, make your boat safer with Fresh Air Exhaust, and much more. Located at our headquarters in Minnesota our Upgrade Division can maximize your time on the water.


Be the first to comment.
All comments are moderated before being published.