South Carolina does not require the kind of winterizing they do in Michigan, and plenty of Lowcountry owners fish straight through December. But most boats around here do sit for a stretch between the last good fall trip and the first warm weekend in spring, and that stretch is where the damage happens.
The threats here are not primarily freeze damage. They are stale fuel, acidic oil sitting against engine internals, dead batteries, and mildew. We do get hard freezes, so the freeze items still matter, but the boats that come in with expensive problems in March almost always failed on the other four.
Fuel: the number one off-season problem
Untreated gasoline starts degrading within about 30 to 60 days, and ethanol blends pull moisture out of humid Lowcountry air the entire time they sit. Come spring, that turns into hard starting, rough running and a fuel system full of varnish.
- Fill the tank to roughly 90 percent. A mostly full tank leaves little room for the humid air that condenses into water. Leave a bit of room for expansion.
- Add a marine fuel stabilizer at the dose on the bottle.
- Run the engine long enough for treated fuel to reach the entire system, not just the tank. Ten to fifteen minutes on the hose is the point of this step.
- Replace the water-separating filter before storage rather than after.
- Use ethanol-free fuel for the last fill if you can find it.
Change the oil before it sits, not after
This one gets done backwards constantly. Used engine oil carries combustion byproducts, acids and moisture. Leave that in the crankcase for four months and it sits against bearings and cylinder walls the whole time.
Change the engine oil and filter before layup so the engine sits full of clean oil. Change the gear oil too, and inspect what comes out. Milky gear oil means water is getting past the seals, and you want to know that in October rather than discovering a corroded gearcase in April.
Flush thoroughly, then trim down
Give the engine a longer flush than usual for the last one of the season. You are clearing salt that will otherwise sit in the cooling passages for months.
Then store the engine trimmed all the way down. Water drains out of the exhaust and cooling passages in that position. An outboard left tilted up holds water inside, and on the handful of nights a year when the Lowcountry drops below freezing, that trapped water is what cracks a housing.
Batteries
A battery left connected and unattended will discharge, and a discharged lead-acid battery sulfates and loses capacity permanently.
Either disconnect the batteries and put them on a maintainer, or leave them in place with a maintainer connected. Clean the terminals before storage and coat them. Do not simply disconnect and forget for four months.
Moisture and mildew
Our humidity does not take the winter off. Mildew is the most common cosmetic complaint we hear in the spring.
- Get the boat completely dry before covering it. Open every hatch and compartment and let it air out first.
- Take cushions home, or at least stand them on edge so air circulates.
- Drain the livewell, the washdown system and any plumbing, and leave lids open.
- Pull the drain plug and keep the bow high so rain runs out.
- Use a cover that breathes and is supported so water cannot pool. A tarp lying flat on the deck traps moisture and does more harm than no cover.
- Moisture absorbers in enclosed compartments help.
Do not forget the trailer
If the boat is going to sit on its trailer for months, the trailer deserves five minutes. Check tire pressure, cover the tires if it will sit in the sun, and take the weight off the tires with blocks or jack stands if you can. Our post on boat trailer maintenance covers the rest, and the off-season is exactly when bearing service should happen.
The best argument for off-season service
Here is the practical reason to do this in the fall rather than the spring: our shop schedule is open in November and full in March.
Everyone remembers their boat needs attention on the first 70-degree Saturday, and they all call the same week. If you bring the boat in during the quiet months, you get it back faster, you are not losing fishing days, and anything we find has time to be dealt with properly. This is also the right window for a repower, since engine lead times are easier to absorb when you are not counting down to the season.
Where the boat sits
Under cover is better than outside. Off the ground is better than on it. Away from trees is better than under them.
If you do not have a good spot, we offer winter boat storage at our facility in McClellanville. Call and ask what we have available, since space is limited and it goes early.
A short version
- Fill the tank to about 90 percent, stabilize, run it through the system
- Change engine oil, filter and gear oil
- Long final freshwater flush
- Store the engine trimmed down
- Batteries on a maintainer
- Everything dry, drained and aired out before covering
- Drain plug out, bow up, breathable supported cover
- Trailer tires and bearings checked
If you would rather hand the list to someone else, we handle layup service at 10129 US-17 in McClellanville, Monday through Friday 8:30 to 5:00. For owners around Charleston and Mount Pleasant who cannot easily tow, some of this can be done at the boat through our mobile service. Call (843) 887-3330 or see our boat service page.
For the full year-round picture, our season-by-season maintenance checklist covers the other three quarters.
Frequently Asked Questions
Do you need to winterize a boat in South Carolina?
Not in the full northern sense, but yes to the parts that matter. Our winters are mild enough that many owners keep boating, yet we do get hard freezes, and the bigger risk here is a boat sitting unused for months with untreated fuel, dirty oil and a flat battery.
Should I change the oil before storing my boat or in the spring?
Before storing. Used oil holds combustion acids and moisture that will sit against internal engine surfaces for months if you leave it in. Changing before layup is one of the highest-value things you can do for an engine that is about to sit.
How should an outboard be stored, tilted up or trimmed down?
Trimmed down, so water drains out of the exhaust and cooling passages instead of collecting inside them. An outboard left tilted up traps water, and in a hard freeze that water can crack a housing.
How long can fuel sit in a boat before it goes bad?
Untreated gasoline can begin degrading in as little as 30 to 60 days, and ethanol blends attract moisture the whole time. If the boat will sit more than a few weeks, add stabilizer and run the engine long enough to circulate treated fuel through the entire system.
Is it better to store a boat with a full or empty fuel tank?
Mostly full, with stabilizer added. A full tank leaves little room for the humid air that causes condensation. An empty tank through a Lowcountry winter collects water on the tank walls, and that water ends up in your fuel system.
