How to Winterize A Boat In All Climates | Great Days Outdoors

How to Winterize A Boat In All Climates

About 71% of our earth’s surface consists of creeks, ponds, lakes, rivers, and oceans. All this water is like a magnet for most kids and adults, and many of us first dipped our toes into this magical substance at a sandy beach or a muddy riverbank. However, chances are some of us water-lovers eventually discovered that a boat could give us access to less crowded, more remote locations. Boats allow us to enjoy being on the water, but only as long as our vessel is operating correctly. Preventative maintenance and knowing how to winterize a boat can play a major role in keeping it seaworthy and all of its systems operating efficiently, with less downtime.


how to winterize a boat

Properly maintaining your boat in the winter months will keep it running great and on the water for many years to come.





Seasonal Maintenance and Winterization Go Hand-In-Hand

A ton of people use their boats in the warmer months and then store them in the off-season or winter months. 

But what if you lived in a tropical or semi-tropical environment where the temperature rarely dipped near the freezing mark? Do you need to know how to winterize a boat? If one is fortunate to live where they use their boats year-round, the term winterizing somehow doesn’t seem to fit.

Winterizing a boat in warmer climates looks different than where freezing temperatures regularly occur. Extra precautions are necessary in colder weather to prevent engines, pumps, and lines from being damaged or cracked from expansion during freezing.



Winterization or Off-Season Maintenance?

It’s hard to take the word winter seriously if you live near Key West, but as long as your routine maintenance gets done, the term you use to describe your boat work doesn’t matter.

A recent Alabama Saltwater Fishing Report podcast featured guest Anthony DelGreco discussing what winterizing a boat and motor looks like in south Florida vs. Minnesota.

Anthony grew up in Jupiter, Florida, and has been around boats and the boating industry his whole life. He now resides far away where winter really is winter, in Vermont but has boated from New York to Maryland and down the Mississippi waterway.


boat stored under tarp

If you are able, storing your boat in a garage of some sort is a great place to start your winterization process.


His extensive boat maintenance and restoration work in various climates make Anthony uniquely qualified to define what winterization looks like in the warmer locales.

I also spoke with Martin Kroesche, the President and CEO of Boaters List. Martin is a USCG Captain who lives in San Antonio, Texas, and his passion is everything connected with boating. His website is an excellent resource for connecting new and seasoned boaters with everything from sales and service to fishing guides, charters, rentals, insurance, and more.

Kroesche shared his insights on what boaters along the Texas coast do in the off-season to ensure their boats are ready when those warm Spring breezes arrive.


How To Winterize A Boat

“Traditional winterization or routine maintenance is done when a boat is going to be parked for an extended length of time,” said Del Greco . “In warmer climates, this would fall into the category of preventative maintenance.”

Both Del Greco and Kroesche outlined a few steps they recommend on how to properly winterize a boat, which will help avoid costly repairs and downtime due to neglect.


Inspecting/Changing Oil

“Accumulated hours usually determine when engine oil changes occur. Still, it’s also a good idea to periodically inspect it by taking a small sample,” Del Greco explained. “A more extreme inspection involves testing kits that go beyond what a visual inspection can detect.”

An oil sample analysis (OSA) can detect the levels and types of metals and the presence of contaminants in the oil of both gas and diesel engines. For example, if any abrasive, soot, water, fuel, or engine coolant shows up in the sample, the lab report will list the possible causes and even offer recommendations.

The analysis will include any abnormal concentration of metals and flag the sample if the viscosity is incorrect. Discovering any of these out-of-range conditions early on can prevent more expensive repairs in the future.


Power Steering and Trim

Your owner’s manual will show where your filler caps are for your trim and steering fluid. It will also show the position your motor and steering cable needs to be in when checking fluid levels.


boat power steering

Be sure to check your power steering during the off months, when your boat isn’t being used regularly.


Follow the directions for your motor to ensure the proper fluid levels are maintained. After break-in, most engines include this as part of the 100 hour or annual list of items to inspect.


Lower Units

Most sterndrive and outboard manufacturers advise changing the gear-case oil in your lower unit every 100 hours or once a year (whichever comes first). Clean lubricant is critical for protecting the gears and preventing expensive damage. Fortunately, servicing the lower unit is a simple job that you can easily do yourself.

Inspect the anodes at this time and replace them if needed. Also, be sure to replace the o-rings or plastic washers behind the access screws. In addition, locate and grease any nearby zerk fittings.

Remove the prop, check for fishing line and inspect the splines and any o-rings for wear. Visually inspect the propeller edges for wear or damage and grease the shaft before reinstalling.


Water Pump/Impeller

If you’ve ever experienced a failed impeller, you realize that it’s cheap insurance to replace your water pump before it becomes brittle or damaged. 

Kroesche also suggested flushing and rinsing your motor after each outing in saltwater to help clear the salt residue and scale that can accumulate in the cooling passages.

The suggested time between inspections is 200-300 hours or three years for deepwater operation. Operating in sandy, shallow conditions will cause premature wear, and annual replacement will most likely be necessary.


Spark Plugs

Inspect your spark plugs every 100 hours and replace them at 300 hours. Your plugs can reveal much about your engine’s health. Specifically, the ceramic firing nose can tell you a great deal about the engine’s overall operating condition. 

Generally, a light tan or gray color indicates that the spark plug is operating at optimum temperature and the motor is running correctly. 


piston rods and seals

Don’t forget about your piston rods and seals.


Wet, dark, or discolored plugs reveal a rich or lean fuel mixture, and you should make every effort to diagnose the cause.


Diesel/Gas Issues

“Today’s unleaded fuels have a short shelf life, Kroesche explained, “They tend to become unstable after just a few months.” 

In addition, he said that any fuel remaining inside an engine during storage could turn into a varnish-like substance that can clog fuel lines, injectors, and pumps. He suggests disconnecting the fuel line and letting the engine idle till it quits.

“Some coastal areas offer ethanol-free fuel, and although more expensive, it’s better for your system in the long term,” Kroesche added. He also recommended keeping your tank full while it’s stored to prevent condensation and using a quality diesel/gas additive to prevent future fuel issues. 

Check the fuel inspection bowl for water before every trip. A clogged raw water or sea strainer is a frequent cause of engine failure on inboard diesel and gas engines. A fouled strainer prevents water from being drawn into the cooling system, so check before each outing.

Change your fuel and air filter annually.



Pounding waves are rough on a boat’s electronics and wiring. The constant flexing puts a lot of pressure on a boat’s wiring. Add heat, chemicals, and saltwater to the equation, and you can see the need for routine inspection

Friction-caused chafing is a leading culprit in many boat fires, and older boats especially require a greater level of inspection to prevent potential wiring issues.

Kroesche recommends disconnecting your battery terminals or utilizing a trickle charger. He also recommended removing all detachable electronics from your boat and storing them in a secure, dry location.

“Use dielectric grease on your wiring connections and splices,” Del Greco said.



I visited with Pat Latham at my local marina (L&L) to discuss how to winterize a boat, preventative maintenance, and some of the issues he’s dealt with over the years. He said that mice, chipmunks, and dirt daubers cause extensive damage to wiring and even engines.

A boat in storage is a magnet to critters looking for a temporary residence. Pat said he’d seen a lot of insulation gnawed by rodents. 


boat under tarp

Tightly wrapping your boat in a tarp will keep most of those pesky critters out of your stored boat.


“I once found a large dirt dauber nest in an engine that was losing power. The nest was inside the plenum, and it went into the intake where the mud damaged the rings and piston. Unfortunately, the owner’s insurance wouldn’t cover the damages, so he was stuck with costly repairs,” Latham said. 

Varmint-proof your boat when it’s not being used.


Clean Everything

Kroesche suggests removing everything from compartments and storage boxes before cleaning and drying. Life jackets, cushions, and first aid kits will get wet and develop mold/mildew.

Afterward, clean the boat’s outer hull. A power washer and the appropriate cleaning solution will remove any scum, algae, or dirt from the exterior. 

Then polish, wax, and use a metal protectant like Corrosion Block to help prevent dirt, rust, and algae buildup.


Final Thoughts

It seems like a lot of work, but knowing how to winterize a boat can save thousands of dollars in repairs by preventing or catching minor issues before they become more significant problems.

P.S.- (Don’t forget about your trailer.)



Boaters List

Martin Kroesche

(361) 510-1070


DelGreco’s Custom Carpentry

Anthony DelGreco

DelGreco’s Custom Carpentry

(954) 684-1227


L&L Marine

(205) 333-1605

Full Disclosure: This post may include affiliate links. There’s no extra charge to our readers for using these.

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